A medium processing device includes a first, second and third conveyance path, a classification section, a first, second and third switching unit, a first, second and third storage box and a controller. Each of the first, second and third conveyance paths has two ends. One end of the first conveyance path is connected to one end of the third conveyance path. One end of the second conveyance path is connected to the other end of the third conveyance path at a second side of the classification section opposite to the first side. The other end of the first conveyance path is connected to the other end of the second conveyance path. The controller controls the first conveyance path and the second conveyance path so that the first and second conveyance paths are driven independently from each other.