PURPOSE: To obtain a heat exchanger constituted of a large-sized roll bond panel by a method wherein a plurality of panels having the refrigerant circuit of the same pattern are combined in arbitrary directions.

CONSTITUTION: Panels 1a-1c are provided with meandering refrigerant circuits 15 while the refrigerant circuits 15 are provided with a prearranged connecting port 3a, provided on one side of the panels 1a-1c and opened in the lengthwise direction of rolling, prearranged connecting ports 3b, 3c, provided on the other side of the panels 1a-1c and opened in the lengthwise diration of rolling, and preliminary prearranged connecting ports 5a-5c, provided in the vicinities of respective prearranged connecting ports 3a-3c and opened in the widthwise direction of the rolling.