A sheet processing device includes a conveying unit, a presser, an end detector, and a setting unit. The conveying unit conveys a sheet having a crease formed therein. The presser presses the crease in the sheet. The end detector detects an end in a conveying direction of the sheet at a position upstream of the presser in the conveying direction. The setting unit sets a crease position where the crease is to be formed. Upon detection of the end in the conveying direction, the conveying unit conveys the sheet to a position where the crease faces the presser, on the basis of the crease position set by the setting unit. The presser presses the crease in the conveyed sheet.