Punching device, conveying device, finishing device, and image forming apparatus

An image forming apparatus comprising:

• a punching device including
• a conveying unit that conveys a recording medium;
• a detecting unit that detects a lateral edge position of the recording medium to obtain edge position data;
• a punching unit that punches the recording medium;
• and
• a moving unit that moves the punching unit in a direction perpendicular to a conveying direction in which the recording medium is conveyed;
• a storage unit that stores therein edge position data obtained by the detecting unit as reference data;
• and
• a controlling unit that determines, 1) an average of previous position data, 2) calculates an amount of registration misalignment, and 3) determines a movement amount of the punching unit based on the reference data stored in the storage unit when the edge position data obtained from the recording medium by the detecting unit indicates an error value.