An overhead image reading apparatus includes an image-capturing unit that captures an image of a medium to be read placed on a placement surface from above, a light source capable of irradiating the medium with light, and a brightness controller that gradually alters brightness of the light source at least when the light source is turned on or when the light source is turned off. The overhead image reading apparatus may gradually alter the brightness by duty control on current supplied to the light source. Or, the overhead image reading apparatus may gradually alter the brightness by controlling a current value supplied to the light source. Alternatively, the overhead image reading apparatus may include a variable aperture between the light source and the placement surface to gradually alter the brightness by controlling an opening area of the aperture.