An image reading apparatus includes a light source and a movable light reflecting surface provided to be capable to move to a first position to reflect light from the light source. The image reading apparatus includes a cam to move the light reflecting surface and having a first portion, a driving module for providing a driving force, and a transmission member for rotating the cam with the driving force provided by the driving module, the transmission member having a second portion, wherein the transmission member moves the light reflecting surface to a predetermined position by rotating the cam, and by bringing the second portion into contact with the first portion to hold the light reflecting surface at the predetermined position when there is no driving force.