A sheet separating device includes: a lifting nozzle configured to blow air against an end portion of a sheet bundle placed on a sheet loading portion to lift sheets; a separating nozzle configured to separate the sheets; a lifting-nozzle shutter member configured to open and close the lifting nozzle; a separating-nozzle shutter member configured to open and close the separating nozzle; a lifting-shutter driving mechanism configured to drive the lifting-nozzle shutter member; a separating-shutter driving mechanism configured to drive the separating-nozzle shutter member; and an open/close control unit configured to control the lifting-shutter driving mechanism and the separating-shutter driving mechanism such that the lifting-nozzle shutter member and the separating-nozzle shutter member are opened or closed simultaneously.