To surely couple two shafts with high accuracy and without misalignment of shaft centers.

A grip member 83 is deeply engaged with a grip force applying member 85, whereby a grip part 83a is caused to firmly hold a rotating driving shaft 82. A coupling part Lc of the grip member 83 in which a rotating shaft 81 is inserted is formed in a symmetrical shape about the center axis CL, and a screw member 94 is passed through the rotating shaft 81 from the outer peripheral side of the coupling part Lc of the grip member 31 to fasten the coupling part and the rotating shaft 81. Thus, the coupling part Lc holds the rotating shaft 81 while deflecting symmetrical about the center line CL, thereby connecting the rotating shaft 81 and the rotating driving shaft 82 to each other with the shaft centers aligned with each other.