A machine tool capable of facilitating a process of mounting a fluid supplying unit to a spindle supporting unit is provided. The machine tool has a rotating unit including a spindle provided with a workpiece chucking unit, a supporting unit which rotatably supports the spindle around a spindle axis, and a fluid supplying unit removably mounted on a rear end of the supporting unit to allow fluid flow inside the spindle toward the chucking unit. The fluid supplying unit has an insert to be received in the rotating unit in the direction of the spindle axis. A labyrinth clearance is formed between the outer circumferential surface of the insert and the inner circumferential surface of the rotating unit when the fluid supplying unit is mounted on the rear end of the supporting unit. The labyrinth clearance allows rotation of the rotating unit and restricts leakage of the supplied fluid from inside the spindle when the rotating unit is rotated.