An image forming apparatus includes: a print head to form an image on a recording medium; a carriage, including the print head, which scans in a main scanning direction; a linear encoder scale with scale marks and elongated in the carriage moving direction to detect a position of the carriage; an encoder sensor disposed on a side wall of the carriage including a groove with an upper open concave-shaped cross-section if seen from the carriage moving direction and reads scale marks on the linear encoder scale by passing the linear encoder scale through the groove; and a through-hole forming member, disposed on the side wall of the carriage, configured to cover the encoder sensor, and forming a through-hole extending in the carriage moving direction which the linear encoder scale is passed through. The through-hole forming member is disposed openable with respect to the carriage.