Several other long-standing members of the board will also step down at next month’s annual meeting.
Chief executive Duncan Fraser, who has worked alongside Mr Milne for 17 years, will leave his position immediately but will remain as a non-executive board director.
Board directors Ian Jack, Duncan Skinner and Craig Brown will also step down to make way for the new investors.
Mr Brown will remain a the club in an ambassadorial role, while Mr Skinner will remain chairman of the board of trustees of Aberdeen FC Community Trust.
Shareholders were issued with details of the changes over the weekend, along with the accounts which reveal a record turnover for the club.
It has increased by half a million from £15.4million to £15.9million, which the club has attributed to a rise in commerical income, more fans coming through the gates and cup competitions. That has been offset by a reduction in UEFA prize monies and a drop in broadcasting income as a result of finishing fourth in the Ladbrokes SPFL Premiership.
