PURPOSE: To form a uniform and superior remelted surface and to perform padding mold, by regulating the shaft line of a torch so that it is always perpen dicular to the tangential line at the cam surface and also holding a distance between the end of a torch and the cam surface constant.

CONSTITUTION: A camshaft 1 is set between a chuck 20 and a rotary center 21. The servomotor 13 for the lateral motion of a torch 10 irradiating high- density energy such as laser beam, TIG arc, plasma arc, and electron beam, a servomotor 15 for the longitudinal motion of the camshaft, a servomotor 17 for the vertical motion of the camshaft, and a servomotor 19 for the rotation of the camshaft are controlled simultaneously, by which the camshaft 1 is allowed to move up and down and the distance between the torch 10 end and the cam surface is made constant, and also, the camshaft 1 is allowed to move back and forth and the angle formed by the shaft line of the torch 10 and the tangential line at the cam surface is made constant. By this method, a camshaft having uniform hardening depth and thickness of padding and excellent in quality can be obtained.