To provide a blank member manufacturing device capable of efficiently cutting blank members to improve the yield of press-molded products.

Blades parts 20a and 21a of a lower blade 20 and an upper blade 21 of a shearing machine 12 to cut plate material 101 in prescribed length in order to form the blank members 100 are composed of edge parts having comb-teeth irregularities. With the blade parts 20a and 21a, comb-teeth irregularity parts 100c are formed in non-machined ranges 100b of edge side parts when the blank members 100 are formed. Part of necessary material for the non-machined ranges 100b cut from the plate material 101a is commonly used. By securing the length of the non-machined range 100b necessary for press work by the irregularity part 100, yield can be improved by improvement in use efficiency of the plate material 101a, and improve yield of the press-molded products 110 simultaneously.