A support member 60 that projects to a sheet conveying direction and supports sheets, which are sorted and discharged, from a rear surface side thereof is provided in a discharge port 7 a of a processing tray 12 or a standby tray 10 . The support member 60 is installed not to interfere with a shutter 52 when the shutter 52 rises. The support member 60 is installed to be inclined upward at an angle equal to or larger than an installation angle of the processing tray 12 or the standby tray 10 . The support member 60 may be formed of a conductor that conducts static electricity and installed in a metal section of the discharge port 7 a.