To provide a water heat exchanger constituted by joining a refrigerant pipe comprising a flat pipe made of aluminum or aluminum alloy and a water pipe comprising a flat pipe opposed to the refrigerant pipe and made of stainless steel together by brazing or soldering, and a method of manufacturing the same such that a joining time is shortened and occurrence of erosion of the refrigerant pipe is suppressed.

A method of manufacturing a water heat exchanger (22) includes subjecting a surface (42) of a water pipe (40) which is opposed to a refrigerant pipe (60) to roughening processing and joining the roughened surface (40) of the water pipe (40) and the refrigerant pipe (60) by brazing or soldering.