A sheet processing apparatus is featured in that a waiting tray comprises
an extensible tray set to enable projection of a transported sheet in a
distal end direction and retraction into a distal end direction, wherein,
in the case where a size of a sheet transported to the waiting tray
exceeds a size set on the waiting tray, an extensible tray drive roller
is driven to project the extensible tray in a transport proximal end
direction of the sheet.