PURPOSE: To easily remove or replace the insert cutter to a rotating body by providing a tightening means so as to be movable toward the rotational axis of the rotating body.

CONSTITUTION: The conical end part of a clamp screw 20 extending in parallel with the contral axis of the rotating body of a cutting machine is engaged with the opening concical surface 24 of a tightening member 16 arranged inside the groove 14 of a supporting body 6 fitted to the body. By feeding of this clamp screw 20, the tightening member 16 is moved inward the rotational axis of the rotating body by the cam action between the conical end part and the opening conical surface 24, so that the insert cutter 8 is firmly pressedly fixed to the supporting body 6. When the insert cutter 8 is to be removed or replaced, the clamp screw 20 is released, and the tightening force of insert cutter 8 being pressed against the supporting body 6 is released, and the insert cutter 8 is drawn out from the supporting body 6 and is replaced.