To provide a technique for holding a tip tool with a simple structure.

A clamp shaft 123 includes a shaft, a clamp head 125, and a locking flange 126. The clamp head 125 and the locking flange 126 are formed projected from the shaft in a radial direction. A clamp shaft holding mechanism 130 includes a circular member 131 which is positioned between the outer end of the locking flange 126 and the shaft, and holds the locking flange 126. The circular member 131 holds the clamp shaft 123 in cooperation with the locking flange 126. Thus, a blade 200 is held between the clamp head 125 and a spindle 120.