A sheet processing apparatus includes a stacking tray for accommodating sheets discharged thereto. A sheet discharging mechanism discharges the sheets to the stacking tray. A moving mechanism reciprocates moves substantially vertically the stacking tray between a first position, which is below the sheet discharging mechanism, and a second position between said first position and the sheet discharging mechanism. A controller controls the moving mechanism to move the stacking tray to the second position when the sheet discharged by said discharging means is discharged through a predetermined distance onto a stacking tray located at the first position.