To provide a device capable of obtaining an object to be worked at a relatively low cost in a short time, the device which works so that the phase of a ridged part and a grooved part in a nose tip part is inverted via a bending part with respect to the phase of the ridged part and the grooved part in a main body part, at the time of forming the main body part and the nose tip part with the bending part interposed in a strip steel and forming the ridged part and the grooved part which extend in the width direction alternately in the longitudinal direction in both the main body and the nose tip part.

The device is provided with a pair of upper and lower stepping rolls, one 3 of the rolls is provided with a first cylindrical part 31 in which the ridged part 31a and the grooved part 31b are formed and a first truncated conical part 32 in which the ridged part 32a and the grooved part 32b whose phase is inverted with respect to the ridged part 31a and the grooved part 31b are formed. The other 4 of the rolls is provided with a second cylindrical part 41 in which the ridged part 41a and the grooved part 41b meshing with the ridged part and the grooved part in the first cylindrical part are formed and the second truncated conical part 42 in which the ridged part 42a and the grooved part 42b meshing with the ridged part and the grooved part in the first truncated conical part are formed.