A method and apparatus are provided for hardening a surface of a cam which forms a chill layer of equal depth on the surface of the cam. The method includes the steps of rotating a cylinder cam and thereby oscillating a holder, rotating a camshaft on which the cam whose surface is to be hardened is located and emitting the high energy toward the surface to be hardened. The cylinder cam which is rotated includes a guide groove which includes at least two straight grooves and at least two `V` shape connecting portions so that `V` shape connecting portions connect the straight grooves and form a continuous peripheral guide groove on a surface of the cylinder cam. The holder which holds the camshaft is oscillated at a constant speed in the axial direction of the camshaft by the rotation of the cylinder cam. The camshaft is rotated in the circumferential direction of the camshaft concurrently with the oscillation of the holder. A torch is provided to emit the high energy to the surface of the cam concurrently with the oscillation of the holder and the rotation of the camshaft.