PURPOSE: To obtain a die having many cavities by subjecting a blank material to wire cutting by electric discharge machining to form a pair of cores, deviating both cores from each other within the plane orthogonal with the cut surfaces and mounting the same to a die block.

CONSTITUTION: A blank material is cut to a sawtooth shape by electric discharge machining to form a pair of cores 3, 4 and the metal in waveform parts 5, 6 is cut off by polishing, etc. The cores 3, 4 finished of polishing are deviated from each other and are combined in the plane orthogonal with the cut surfaces in such a way that the one side face of the waveform part 5 contacts with one side face of the other waveform part 6. The combined cores are mounted to a die block. Cavities 7 independent from each other are formed between the cores 3 and 4 in the above-mentioned way. The die having the many cavities between both cores are thus obtd. at one time.