The present invention provides manufacturing method of a heat exchanger that, even if the position of a tube opening portion of a tube of a heat exchanger for which tube expansion is conducted, varies depending on the type of a heat exchanger, a mechanism adjusting the stop position of a flare plate as well as any complicated adjusting work therefor are not necessary and a heat exchanger in which flares in the same shape and in constant certain depth are formed at an opening portion of a tube of various kinds of heat exchangers having different total lengths in the longitudinal direction, and a device for a heat exchanger manufacturing method, and an air conditioner and/or outdoor unit thereof equipped with a heat exchanger manufactured using said manufacturing method.