A carriage for an image scanning unit which scans an image on an object is provided with a light source, a reflecting member placed to face the light source and configured to reflect a light emitted from the light source toward the object to illuminate the image, a housing that contains the light source and the reflecting member, the housing having an opening which allows the light reflected by the reflecting member to pass through and proceed toward the object, and a radiation plate connected to the reflecting member so that heat is conducted from the reflecting member to the radiation plate, at least part of the radiation plate being exposed to outside the housing.