PURPOSE: To surely and sufficiently guide, suck, and discharge chips without being scattered.

CONSTITUTION: Each throwaway tip 23 is installed to a recessed groove 22 on the top end outer circumferential part of a cutter body 20 by a clamp member 26. Each clamp member 26 has a chip guide part 28 whose end surface is formed by a notch 29 opposed to the face of the tip 23. A clearance (t) for allowing the pass of chips is formed between the notch 29 and the tip face. A chip sucking cover 40 is mounted on the outer circumference of the cutter body 20, and a chip housing chamber 42 to which the chips are guide from the clearance (t) is provided between the both. The chip guide part 42 is situated to cover the top end opening part of the recessed groove 22 with clearances being left with the tip face and with the top end inner circumferential surface of the cover 40, respectively.