An image forming apparatus includes an optical scanning unit having a light transmitting portion, the cleaning mechanism that includes a cleaning rod with a pad at a front end portion thereof to be capable of cleaning a surface of the light transmitting portion by sliding on the light transmitting portion, and a retaining mechanism that retains the cleaning rod slidably in a longitudinal direction of the light transmitting portion, and that retains the pad positioned above the optical scanning unit and spaced apart from the optical scanning unit in a state where the cleaning rod is at an insertion completed position.