An apparatus includes a transport path for transporting a sheet, a branch path branched off from the transport path to transport a sheet to a stacker, transport rollers on the transport path, branch rollers on the branch path, and a sheet processing control section controlling the rollers. The control section performs wait transport for switchback-transporting a sheet to cause the sheet to once wait in the branch path after the sheet transported in the transport path passes through a branch position, and transporting the sheet to a first processing tray together with a subsequent sheet, and second tray transport for switchback-transporting a sheet to transport to the stacker via the branch path after the sheet passes through the branch position, makes a switchback transport velocity in the second tray transport lower than that in switchback transport in the wait transport, and suppresses fluttering and bending of the sheet.