New figures show more than 18% of graduates now achieve the top award, compared with fewer than 16% in 2006/07.
Over the same period the proportion achieving a first or a 2:1 has grown from 68% to 72% – the highest in the UK.
Liz Smith, education spokeswoman for the Scottish Conservatives, said the rise would cause confusion.
She said: "There are some outstanding students in our universities, but the public remains confused as to why these increases come when employers are persistently complaining that many graduates do not have the relevant skills."
However, Alastair Sim, director of Universities Scotland, said the figures were the result of improving school exam grades and higher entry tariffs from institutions.
He said: "Universities have, for several years now, been able to select from applicants with ever-improving Highers results.
"This has been reflected in an increase in entry requirements at some universities."