Deputy First Minister Nicola Sturgeon confirmed that an independent Scotland would have to negotiate for EU membership during a speech in Brussels.
The SNP deputy leader said that Europe would benefit if Scotland continues to be in the EU if it votes for independence in next year's referendum.
During her speech she highlighted her "deep concerns" about Prime Minister David Cameron's plans for a referendum on UK membership of the EU after 2015.
Addressing an invited audience of European Policy Centre members, Ms Sturgeon spoke about the "massive opportunities that European Union membership brings".
But she warned: "Instead of leading the EU, the UK is in danger of sleepwalking towards the exit. Such an outcome for Scotland would be contrary to public opinion and against the public interest."
Her "hope and expectation is that before the UK Government holds its planned referendum, Scotland will have become an independent nation".
Negotiations over an independent Scotland's membership of the EU would start "as soon as possible" after a Yes vote in the referendum, the SNP deputy leader said.
The UK Government has said that a vote for Scottish independence would lead to the country being ejected from the EU and forced to reapply for entry as a new state.
Ms Sturgeon said the Scottish Government "does not take the process of EU membership for granted".
She said: "We understand that it is essential to respect the legitimacy of existing EU treaties. We also understand that our continued membership will require negotiations, and the agreement of other nations."
Europe as a whole would benefit if Scotland continues to be a member and an independent Scotland would begin negotiations "as a nation which would be a net contributor to the EU budget, and whose people are already EU citizens".
Scotland "already applies the body of EU law and policy" and, if independent, would be "keen to be an equal and constructive partner in the EU", she said.
Scotland would seek to retain the UK's existing opt-outs from the euro and the Schengen free-travel agreement.
"On issues like the euro, Schengen and the rebate, our aim would be to retain the prevailing terms of Scotland's membership," she told the audience in Brussels.
"There is, of course, much discussion of law and process in this debate. But ultimately, the most powerful case for Scotland's continued membership is not based on law or process but on common sense, reality and mutual self-interest."
Ms Sturgeon highlighted the "potential importance of Scotland's natural resources to the European Union", saying: "We have the major share of the EU's oil production, almost a quarter of its offshore renewable energy potential, a fifth of its natural gas production and a 12th of its seas.
"Perhaps most importantly of all though, in addition to the contribution we can make through our natural resources, our research capabilities and our policy interests, there are five million people in Scotland who benefit from and contribute to the free market and freedom of movement that the European Union provides. They are already European Union citizens and overwhelmingly wish to remain so."
It would "benefit absolutely nobody" if an independent Scotland was not in the EU, she said.
If there is a gap in Scottish membership, "new negotiations would be needed to allow other EU fleets to fish in Scottish waters" and that 150,000 other EU citizens living in Scotland would "would face uncertainty about their future status".
She said: "It would be simpler, fairer and more efficient for all nations if people in Scotland could retain the status that they overwhelmingly desire: as citizens of the European Union and proud and constructive partners in the European family.
"After independence we intend to remain part of the European family. And it is why Scottish membership of the European Union will be good for us, good for your individual nations and good for Europe as a whole."
A Scotland Office spokesman said: "The Deputy First Minister's speech finally acknowledges that an independent Scotland would have to notify the EU ahead of negotiations and accession would need agreement of all member countries. This is a major concession.
"The UK Government recently published our view, backed up by legal advice, that confirmed Scotland would not automatically gain entry as a new member state. Our position was consistent with comments by the president of the European Commission and various EU foreign ministers.
"Now that the Scottish Government has at last accepted that there is nothing automatic about an independent Scotland's EU membership, they should explain what is at stake. Terms would also be subject to negotiation with the rest of the EU and would not be inherited.
"Leaving the UK family and putting the terms of Scotland's EU membership at risk would be harmful to Scotland's interests. The UK Government will not do the Scottish Government's work for them by planning for that outcome.
"It is for the Scottish Government to explain how it would propose to negotiate separate EU membership, the terms it would seek and how it would persuade at least 27 separate member states to accept them."
Tory leader Ruth Davidson said: "First the SNP said automatic EU entry would be a certainty, then it was downgraded to a negotiation. Now Nicola Sturgeon is trying to pretend the Scottish Government has never taken EU admission for granted. But its behaviour over the past 12 months indicates the complete reverse.
"If the Scottish Government was never complacently banking on entrance to Europe, why did Alex Salmond dupe the people of Scotland about seeking legal advice?
"The Deputy First Minister has today gone to great effort to convince European nations that she and Alex Salmond have thought deeply about the matter, but the evidence suggests anything but."
Liberal Democrat MEP for Scotland George Lyon suggested the "negotiations for an independent Scotland's entry to the EU would be closer to 16 years than the 16 months that the Scottish Government has asserted".
He said: "Since the start of the independence debate we have had nothing but smoke and mirrors from the SNP on the EU. Firstly Nicola Sturgeon asserted membership would be automatic. Now the Deputy First Minister tells us that we would have to negotiate.
"The SNP have become adept at moving the goalposts to suit themselves but this approach can only take them so far. The SNP need to face up to reality and accept that they would not get everything that they want from membership talks."
