The 21-year-old has joined the 2010 Champions League winners on a five-year contract that runs to June 2018.
"Inter are a great team, I'm really delighted and I hope to do well here," said the player who came through the ranks at French club Lyon.
Last season Belfodil scored eight goals in 33 matches for Parma.
Inter Milan have sign Algerian forward Ishak Belfodil from fellow Italian Serie A side Parma for a fee believed to be about US$13m.