PURPOSE: To adopt the motion of a hammer to the passing speed and forging conditions of a material to be worked by controlling the motion of a rocking arm which is bent at approximately 90° to the hammer shaft in a range of a guide which is provided at the free end of the arm.

CONSTITUTION: Respective forging hammers 2 are extended in the radial direction to eccentric rotary shafts 4, provided with the rocking arms 7 which are bent at approximately 90° to the hammer shaft and the motion of these rocking arms 7 are controlled in the regions of the guides 8 which are provided at the free ends of the arms. Because each hammer 2 has an own rocking arm 7, a ring-shaped hammer body with which the eccentric rotary shaft 4 is surrounded is adequate, the size of a forging machine 1 is reduced and desirable balance of force is generated. Moreover, by taking the suitable guide 8 of the rocking arm 7 as a means and overlapping additional motion which is situated in the passing direction of the material 5 to be worked on the limited motion of the hammer 2 with the eccentric rotary shaft 4, more increase of the degree of freedom is possible. Consequently, the rocking motion and speed of the forging hammer 2 in operation are adapted to the forging conditions each time.