Patent ID: 8016280

Claim:
A sheet processing method comprising: arranging a hole punching section orthogonally to a conveying path of the sheet, in order to perform punching processing to a sheet conveyed thereto, and enabling the hole punching section to move along the orthogonal direction and in a direction toward a retreat position and a punching processing position; providing a detection unit configured to move by being interlocked with the hole punching section, upstream from the hole punching section, in order to detect a lateral edge of the sheet conveyed thereto; changing tilt angle of the hole punching section in accordance with a quantity of skew of the conveyed sheet; moving the hole punching section in a first direction toward the retreat position along the orthogonal direction to the conveying path when the sheet is conveyed in the hole punching section; in the process of moving the hole punching section in the first direction, when the detection unit has detected the lateral edge of the sheet, moving the hole punching section from there in the first direction by the prescribed quantity that is preset, and causing the hole punching section to reach a standby position, the standby position is between the retreat position and the punching processing position; moving the hold punching section from the standby position into a second direction opposite to the first direction, and controlling movement to the punching processing position in accordance with the result of detection by the detection unit; and performing punching processing to the sheet at the punching processing position.