كتب : Ahmad Saied
A Celtic supporter stormed into the pitch after the hosts scored a stoppage-time winner and seemed to be hitting Dida in the face.
Although it appeared as a slight touch, the Brazilian keeper took two steps in chasing the invader before collapsing theatrically on the floor.
He was stretchered off the pitch and charged by UEFA's disciplinary body of overacting.
Media reports said that Milan are set to appeal the punishment that means Dida will miss both home and away games against Shakhtar Donetsk.
Celtic were found guilty of "improper conduct of supporters" and "lack of organization."
They serve a two-year probation period during which the Scottish Champions will pay a similar fine if the incident reoccurred.