PURPOSE: To reduce working time and to eliminate waste of material by inserting a bar material into a die from the other end of the die and forging the bar material thereby forming an attaching groove.

CONSTITUTION: A die K is attached to a die attaching part 2 and a bar material 20 is successively inserted into the die from the other end side of a die 6. The end face of the material 20 contacts with one side 8 formed to the wedge shape of a groove forming punch 5 and when the material is pressed as it, the attaching groove is gradually formed by forging. A part of the material 20 displaced by the punch 5 extends toward the top end 22. The top end 22 of the material 20 contacts with the top end 23 of an ejector bar 17 and the pressing of the material 20 is completed at the point of this time. The die K is removed and the material 20 formed with the attaching groove is completed.