A hydroforming method for metal produces hardware having a throat in only one side and having approximately right-angled corners without causing thinning and breakage. The method includes using a working fluid to exert a liquid pressure on a metal embryo and cooperating with a push rod of a hydroforming mold to supply material from the lower edge, forcing the side sheet metals to bulge. Furthermore, by using the hydroforming mold to provide a downwardly pressing active force on the metal embryo, under feeding of the downwardly pressing active force cooperating with continuous liquid pressure, the metal embryo deforms and bulges such that each corner of the metal embryo and the wall corners of the die cavity of the hydroforming mold have approximately the same angles. Hardware, every angle of which approximates a right angle, can be obtained after removing the hydroforming mold. This method can also be used to obtain a metal box.