To provide a sheet discharging device, capable of enhancing the stacking alignment property when discharging sheets and preventing damages on the sheets, a sheet processing device and an image forming device.

A stiffness-providing solenoid 201 is controlled according to the discharging mode selected based on information in the sheet pressing direction. A state of a stiffness-providing unit 200b for providing stiffness to sheets to be discharged is changed to a stiffness-providing state of providing the stiffness to the sheets and a stiffness-releasing state of releasing the stiffness to the sheets.