The invention relates to the technical field of heat exchangers, in particular to a heat exchanger manufacturing method and a heat exchanger. The method comprises the following steps: a fin sleeves along U pipe to form a heat exchanger prefabricated part; liquid-state aluminum is poured in the heat exchanger prefabricated part; and the heat exchanger prefabricated part is dried after pouring of the liquid-state aluminum to manufacture the heat exchanger. The heat exchanger manufacturing method, on the one hand, can finish machining of the heat exchanger without needing pipe expansion, and onthe other hand, cannot cause deformation of inner teeth of the long U pipe and contact heat resistance caused in the pipe expansion process to improve the heat exchange performances of the heat exchanger.