The tank main body of a header tank of a condenser has slits formed in a circumferential wall thereof at positions between opposite end surfaces of the circumferential wall and heat exchange tubes at the opposite ends. Plate-shaped closure members are inserted into the slits from the outside of the tank main body and joined to the circumferential wall of the tank main body. Drain openings are formed in the circumferential wall of the tank main body at positions on the outer sides of the closure members as viewed in the longitudinal direction of the tank main body. A portion of a surface of each closure member which faces outward in the longitudinal direction of the tank main body forms a portion of a peripheral edge of the corresponding drain opening.