To provide a sorting device capable of sorting sheets without requiring a complex mechanism.

A sheet sorting device 5 comprises a discharge tray 57 arranging a sheet recorded by an image forming apparatus. A travel roller 53 moves the sheet in a traveling direction in which the sheet is discharged to a discharge tray. A sorting roller 34 moves the sheet in a sorting direction perpendicular to the traveling direction. A left sheet detection sensor 51 and a right sheet detection sensor 52 are provided at the positions with different sorting directions and detect the sheet in the position where the sheet is discharged to the discharge tray 57. A control part causes the travel roller 53 and the sorting roller 54 to be rotated on the basis of detection results of the left sheet detection sensor 51 and the right sheet detection sensor 52 to sort the sheet to a plurality of sorting positions in the sorting direction.