To perform finishing of the inner periphery of a worked hole and chamfering of the bottom surface by one throw-away tip and to accurately and easily perform adjustment of the position of the throw-away tip.

A throw-away tip 10 having a front face cutting edge part 12 inclined to the rear end side toward the tool outer peripheral side and an outer peripheral cutting part 14 continuous with the outer periphery of the front face cutting edge 12 is removably attached on the outer periphery of the tip of a tool main body 1 to be rotated around the axis O. An outside diameter adjusting mechanism 17 for adjusting the position of the throw-away tip 10 in the direction along the front face cutting part 12, and a front face adjusting mechanism 16 for adjusting the position of the throw-away tip 10 in the direction perpendicular to the front face cutting edge part 12 and toward the tool tip side are provided on the tool main body 1.