A first heat radiation unit is formed on one surface of the imaging unit in a vertical direction. A second heat radiation unit is formed on the other surface of the imaging unit in the vertical direction. A third heat radiation unit is formed on a surface opposite to an imaging direction of the imaging unit. A first heat transfer unit transfers heat of a first heat source of the imaging unit to the first heat radiation unit and the third heat radiation unit. A second heat transfer unit transfers heat of a second heat source of the imaging unit, which has a higher maximum allowable temperature than the first heating unit, to the second heat radiation unit. A heat insulation unit suppresses heat transfer between the first and the second heat radiation units and between the third and the second heat radiation units.