His side's reward for their memorable win over Groningen last week is a tie against a side that was in the Champions League group stages last season.
The Basque club have since strengthened with the signing of former Celtic target Alfred Finnbogason, who was the top goalscorer in the Netherlands last season with Heerenveen.
But McInnes believed in his team ahead of their trip to Groningen last week, and he will do so again when they face a much sterner test this evening.
His optimism is further fuelled by the fact his players have had the benefit of four competitive games, having beaten Daugava Riga 8-0 in the first qualifying round, while Sociedad open their season against the Pittodrie side.
"Real Sociedad is a strong name in European football and I think La Liga is regarded, by most, as the best league in Europe," said McInnes.
"Any team that qualifies for Europe from La Liga has to be taken seriously, they are obviously a very good side, with a good tradition and we are delighted to be playing against them.
"We want to do the best we can. On the field, we're in a very good place just now - physically we look good and we look confident - and we take the confidence we have built up into this game."
McInnes, whose side beat Celtic twice last season, added: "Like any cup competition, the further you progress the tougher the opponents and obviously we face a very tough opponent, but we have confidence in our own abilities as a team and we felt that last season.
"Whether we are the underdogs, and we are in this game of course, or favourites like we were in the first round, our approach is always to have confidence in what we do, our players want to show themselves in a good light.
"I think from our point of view we'd rather go into a game of such importance having played competitive games, and obviously we have that advantage over Real Sociedad, but we understand the level of opponent we are up against.
"It is a very difficult game for us but we plan to make it a difficult game for them too. We're not here for a holiday, we're here to try and do well and compete in the game. It's a challenge I feel we're ready for.
"The ideal result is to win, but to score - with the away goal - could also be very important for us."
Jagoba Arrasate, the Real Sociedad head coach, recognises that his side are not at their peak but feels they are ready to adapt to the challenge of their opponents.
"We're not at 100%," he admitted. "That's understandable at this stage of the pre-season, but we are in condition to compete.
"Aberdeen are a typical Scottish side - a hard-working team who work together as a unit and who never give up a game for lost.
"We were able to watch them against Groningen - they controlled much of the game and moved the ball about well.
"They are a versatile team who can adapt to different situations, playing long balls when they need to or playing five at the back; but what really defines them is that they are a highly competitive team.
"We have to take the initiative and take the game to them. Ideally, we would like to have some kind of advantage to take into the second leg in Aberdeen.
"But this is football and we know that this is not going to be easy."