PURPOSE: To arrange the paths of both a main circular saw and a sub-circular saw accurately in conformity with the position of the main circular saw using the sub-circular saw as a reference by forward moving or retreating a screw section by screwing and moving the position of the sub-circular saw in the axial direction of a spindle when a holder is turned and operated.

CONSTITUTION: A locknut 15a and a clamp screw 17 are loosened and the connection of a holder 12b is disconnected, and the holder 12b is rotated and operated. The holder 12b is shifted in the axial direction of a spindle by the rotational operation, and the holder 12b is forward moved by screwing in the direction of the arrow F, thus compensating the displacement size of two circular saws. The clamp screw 17 is operated after the adjustment of the displacement size, a screw section 14 is clamped by the action of a slot section 16 while being screwed until the screw section 14 is abutted against the locknut 15a and a clamping plate 13b, and the positions of saws are fixed through the holder 12b. Accordingly, when the paths of the two circular saws 20a and 20b are confirmed accurately and a machining material is making-worked and cutting-worked, ideal machining generating no crack and burr can be conducted.