A sheet processing apparatus includes a first stacking portion on which a sheet conveyed by a conveying portion is stacked, a binding portion which forms, in a sheet bundle stacked on the first stacking portion, a tongue cut out from the sheet, with a part of the tongue attached to the sheet, and a slit, and which binds the sheet bundle by inserting a tip of the tongue of the sheet bundle in the slit of the sheet bundle, and a second stacking portion on which the sheet bundle bound by the binding portion is stacked. In the sheet processing apparatus, a plurality of recessed parts is formed on a guide face of the binding portion, the recessed parts extending in different directions from each other.