To provide a medium processing apparatus that reliably separates media 20 overlapped with each other and detects overlapped media regardless of variation of thickness of overlapped media 20 without providing other separation mechanism.

A medium processing apparatus 1 includes a turn over section 5 and carries out a predetermined processing while turning over pages of a book-like media 20 like a bank note. The turn over section 5 is adapted to separate pages of the media 20 overlapped with each other and to measure the length of the separated media 20 to detect media overlapped with each other. Further, a second press roller 7b, which faces a second transporting roller 2b, and which is located at the upstream side of a transportation path of a turn-up roller 8 in the turn over section 5, is adapted to rotate in a direction away from a transportation path 9.