To perform cutting by one cutting edge without contacting with a groove bottom face formed by the other cutting edge and restrain formation of a stress concentration part by letting the tooth crest of two cutting edges cooperate with each other, and forming a sectional form in which the groove bottom face and a pair of groove sides formed in a work are smoothly connected together.

A broach main body and a shell blade machining part are mounted on the same shaft, and roughing blade and groove bottom finishing blades as cutting edges and shell blades as different cutting edges from the former are provided side by side. In this case, in relation of the cutting edge form of a final cutting edge 120 within a plurality of groove bottom face finishing blades with the cutting edge form of a final finishing blade 122 for finally finishing a pair of groove sides 76 within a plurality of the shell blades, by letting the cutting edge face 72 of the final cutting edge 120 and the cutting edge face 70 of the final finishing blade 122 cooperate with each other, the groove bottom face 74 and a pair of the final groove sides 76 (between a pair of teeth) in a work 12 are formed into the sectional form of smooth connection actually without sharp angle parts therein.