A screwdriver bit holder structure, whose holder body has a polygon hole, and inside the polygon hole set an inner spring and a sliding tube. The holder body is clipped by a c-clamp, ahead of which are symmetric front balls and holes, and behind which are symmetric middle and back balls and holes. A fixing cap is capped on the holder body. In the back of inner hole of the fixing cap sets a limiting ring, and in the front sets a front recess and a back recess that is designed, by sliding the cap forward and backward along the holder body, to push front balls to fit into the fitting concaves of the bits so as to fix them tightly with the holder body or loose front balls from fitting concaves to release the bits.