PURPOSE: To prevent a vis from remaining in or being caught in the chuck thereby to prevent the bit from being broken, by adapting the chuck for holding the vis to be raised before the bit is raised.

CONSTITUTION: The chuck 6 including the holding portion 5 to hold a vis c is fixed to the block 23 which retreatable from the position d where the vis is to be screwed in. The vis tightening member 4 is attached to a traveling frame 3 which is vertically movable, and the vis tightening member 4 is capable of causing the bit 2 to move toward or away from the position d where the vis is screwed in accordance with the vertical movements of the traveling frame 3. In the present vis tightening apparatus, the chuck 6 and the vis tightening member 4, at the start, are in raised positions and the bottom end of the bit 2 is just above the guide hole 30, and when a vis c is supplied, the chuck 6 is lowered by elongation of the cylinder 24 to approach the position d where the vis is to be screwed in. Then, the frame 3 is lowered and the vis c is screwed in. Thereafter, the chuck 6 is raised by contraction of the cylinder 24 before the bit 2 is raised.