A sheet processing apparatus includes a sheet tray on which one or more sheets to be processed are placed, an adhesive applying unit, and a pressing member. The adhesive applying unit has an end portion that faces the sheet tray and holds an adhesive material and is configured to move towards the sheet tray up to a position at which the end portion is in contact with or proximate to a sheet on the sheet tray and apart from the sheet tray. The pressing member is configured to move into and out of a moving path of the adhesive applying unit. The pressing member is pressed against a sheet on the sheet tray by the adhesive applying unit, when the pressing member is in the moving path of the adhesive applying unit and the adhesive applying unit moves towards the sheet tray.