A medium processing device includes: a drum that has a circular cylinder shape and that rotates about a rotation shaft; a tape that, together with a medium, is wrapped onto a drum circumferential face, this being a circumferential face of the drum; a reel onto which the tape is pre-wound, and from which the tape is pulled out accompanying rotation of the drum; and a rotation restriction mechanism. The rotation restriction mechanism includes a restriction section that is obstructed from moving by the tape wrapped onto the drum circumferential face, and that moves when the drum rotates in an unwind direction to unwind the tape such that the tape comes away from the drum circumferential face to expose a wrapping location of the tape onto the drum circumferential face, and a stopper section that abuts the restriction section so as to restrict rotation of the drum in the unwind direction.