To provide a heat exchanger for hot-water supply, which is prominent in resistance to I-type pitting and facilitated in working to obtain the heat exchanger for hot-water supply while permitting the shortening of a manufacturing process, and the manufacturing method of the same.

An Sn (tin) film, having the thickness of 0.5-3 μm, is formed on the internal surface of a copper tube or a copper alloy tube for hot-water supply and the maximum temperature range upon brazing in a furnace is limited within 750-950°C while heat treatment, retaining the temperature in the range for 1-10 min, is applied to provide a Cu-Sn alloy layer containing Sn by 7-23% on the internal surface of the copper tube or the copper alloy tube for hot-water supply with the range of thickness of 3 μm or more and 50 μm or less.