PURPOSE: To enable outer peripheral surfaces in respective cams on both cam shafts to be finished and processed by grinding by a single cam shaft grinding machine in a DOHC-type internal combustion engine formed by arranging the cam shaft for an intake valve and the cam shaft for an exhaust valve on the upper front surface of a cylinder heat so that they may be mutually and reversely rotated.

CONSTITUTION: A power transmitting ring attaching flange part 3 is provided on one end in one side cam shaft 1, and a flange part 8 having the approximately same size and same shape as the power transmitting ring attaching flange part 3 is provided on the other end in the other cam shaft 2.