A holding member that holds an optical print head for exposing a photosensitive drum is provided with one abutting pin at each end thereof in the longitudinal direction. Each abutting pin has both a function of forming a gap between the optical print head and the photosensitive drum, and a function of restricting movement of the holding member in the X direction and Y direction. The holding member is supported by a link member further toward the side of the photosensitive drum than the lower end portion of the abutting pins.