PURPOSE: To reuse most of a tool main body even if a cutting edge tip is abraded so as to lower a cost.

CONSTITUTION: In a tool main body 2 of a reamer 10, a chip discharging groove is formed parallelly to the rotation axis line O. The tool main body 2 is divided into two parts, and a front end part 11 provided with a cutting edge tip 6 on the front end outer circumference side and a shaft part 12 provided with no cutting edge tip 6 are connected to each other so as to be fixed by means of a fixing screw 17. On respective connecting faces 11a, 12a between the front end part 11 and the shaft part, 12, uneven faces 14, 15 are formed radially while setting screw holes 13, 16 concentric to the rotation axis line O as centers so as to fit both of the connecting faces together.