PURPOSE: To make a throw away tip automatically exchangeable, by providing a mechanism for successively pushing out a tip from the magazine that contains an unused tip.

CONSTITUTION: A magazine 10 is in-out freely contained in a magazine hole 11, provided in a lengthwise direction in a cutting tool main unit, and an unused tip A2 is housed. The tip A2 is pushed out one by one toward front by a pushout plate 14. The push-out plate 14 is provided with a ratchet mechanism 16, 17 for forwarding a tip push-out unit 15 and the tip one by one. With a feed bar 24 forwarding and a protrusion 25 hitting a front nut 26, a step forwarding mechanism 18 is forwarded by s step of one tip together with the feed bar 24, and the tip is shifted onto a rail 28 from the magazine 10 by the push-put plate 14, and replaced with a worn tip A1 of the feed bar 24.