When a lever is pulled upwards, an engaging member comes into contact with a retracted contacting member. An optical writing device rotates with a hooking member at a center and is lifted. As a result, positions of a first reference position component and a second reference position component switches from a contacting position to a retracted position. When the lever is pulled downward, the engaging member separates from the retracted contacting member. The optical writing device rotates in a counter-clockwise direction with the hooking member as the center. As a result, the positions of the reference position components switch from the retracted position to the contacting position. The reference position components come into contact with positioning members.