A sheet sorting device includes three or more trays including a predetermined tray detachable from an apparatus main body and a tray different from the predetermined tray, a discharge unit to discharge a sheet to any one of the three or more trays, a control unit, and a tray detection unit to detect that the predetermined tray is detached from the apparatus main body. The control unit sets a sheet discharge destination such that a sheet conforming to a preset condition is discharged to the predetermined tray through the discharge unit. Where the tray detection unit detects that the predetermined tray is detached from the apparatus main body, the control unit sets a sheet discharge destination that has been set to the predetermined tray to the tray different from the predetermined tray based on a state of each of the trays other than the detached predetermined tray.