A medium processing apparatus includes a printer, a supporting member having a sheet-like shape and configured to support a discharged medium, and a winding unit configured to wind the supporting member and move with respect to the printer. The winding unit has a first case and a second case that rotatably support a winding shaft, and a placement portion placed at a flat surface. The first case and the second case in a state where axis lines of respective bearing portions that support the winding shaft are aligned with each other and in a state of being held so as to be mutually non-rotatable in a plane orthogonal to an axis line of the winding shaft, and when the winding unit is installed on a flat surface, the placement portion contacts the flat surface.