To obtain a fine embossed shape not leaving R of the bottom part of the embossed shape or fine surface roughness caused by the feed accuracy of a precise lathe or the size of R of the leading end of a diamond bite.

A master mold having a fine embossed surface reverse to the fine embossed surface required in a molded product is produced and electroforming processing is applied to the fine embossed surface of the master mold to produce an electroforming mold which is, in turn, released from the master mold to obtain an injection mold. When the recessed part corresponding to the height of the projected part required in the injection mold, a recessed part is processed so as to become at least deeper than the height of the R part left on the bottom side of the recessed part as compared with desired depth and, until the projected part of the electroforming mold formed by reversing this recessed part becomes the height of the projected shape required in the injection mold, the projected end surface of the electroforming mold is removed.