To provide a rotating tool eliminating a dead point of machining and allowing through-machining up to precision machining by the same machining device without using a control program for inclining the axis of a tool body.

This rotating tool has a machining part 7 at the tip part of a tool body 1 and grinds with the machining part 7 brought into contact with a machined surface. At least the part, coming in contact with the machined surface, of the machining part 7 is formed in a projecting surface 8a of circular arc shape, and the tip part of the tool body 1 is provided with the machining part 7 tiltably through a transmission part 5 for transmitting the rotation of the tool body at constant velocity. When machining resistance is applied to the transmission part through the machining part 7, the machining part 7 is tilted from the axis S of the tool body 1.