A heat exchanger is provided to increase heat exchange efficiency by distributing heat exchange media uniformly and preventing the local concentration of the heat exchange media. First and second header tanks(10) are respectively formed with connection parts(70) by cutting. The connection parts include slant portions for connecting neighboring divisions(15) to each other in the width direction of the header tanks. The slant portions are inclined toward an overheating section of the heat exchanger for sending heat exchange media to the overheating section.
