To machine even a small-diameter pipe without interference between bytes, to facilitate carrying out of chips and to improve the rigidity of each byte.

This work machine includes an outer surface machining byte, and end surface machining byte 43L and an inner surface machining byte 45L provided in a byte holder 39L, and the outer, end and inner surfaces of a pipe WG are chamfered by these bytes. In the center part or the offset position of the inner machining byte 45L and the byte holder 39L, a hole 51 is formed in an axial direction, the inner surface cylindrical machining byte 45L is inserted into this hole 51, and an inner surface machining byte adjusting member 55 for adjusting the tip position of the inner surface machining byte 45L is provided in the rear side of the hole 51.