To provide an adapter for fixing a screwdriver that can allow connection of screwdrivers sold in the market with a variety of shape, sizes, bit kinds and the like to a screwdriver with rotation assistance so as to meet preference of an individual, to improve versatility and convenience, and to solve the problem that the screwdriver with rotation assistance is usable basically only with an exclusive screwdriver, or more specifically, a driver connection part of the screwdriver with rotation assistance is square so as to facilitate transmission of rotational assistance force with a fixed size and therefore the adaptable screwdriver is limited to one with the square connection part matching thereto and only of a size corresponding thereto which is not enough from the versatility viewpoint.

The adapter securely holding and fixing the screwdriver of a variety of shapes is manufactured. With the adapter, many kinds of screwdrivers can be used in the screwdriver with rotation assistance and the like.