The invention discloses a manufacturing method for a heat exchanger. The manufacturing method comprises the steps that 1, stainless steel plates are pressed to form heat exchanging plates through a cold pressing die, wherein the heat exchanging plates are provided with groove structures, water inlets and water outlets; 2, the two heat exchanging plates are subjected to butt-weld after being symmetrically combined, and heat exchanging unit bodies where water flow passes are formed; 3, the surfaces of the multiple heat exchanging unit bodies are coated with copper or nickel brazing solder; 4, the multiple heat exchanging unit bodies coated with the copper or nickel brazing solder are orderly arranged and combined and then calibrated through clamps to form a heat exchanger core; 5, the heat exchanger core is placed in a vacuum brazing furnace for brazing, and then a finished product is obtained. Material ingredients of all components are evenly distributed, content of impurities is small, strength is high, airtightness is good, cost is low, the heat exchanger is well formed, even in tissue, high in tensile strength, long in service life, easy to manufacture and high in yield, the overall process cost is low, and large-scale production can be carried out.