A radiator includes a header including a supply chamber for a coolant to cool an electronic part mounted on a circuit board and a discharge chamber partitioned from the supply chamber, and a plurality of tubes stacked in a heightwise direction of the header, one end of each of the plurality of tubes being connected to the supply chamber and the other end of each of the plurality of tubes being connected to the discharge chamber, and the coolant flowing from the one end to the other end. The plurality of tubes include a first tube at least including a lowermost tube, and a second tube provided over the first tube and having a surface area greater than that of the first tube.