PURPOSE: To improve an efficiency of charging an air chamber with air by constituting an air pump so that more air can be fed even from operational force same in the conventional device or the operational force can be lightened.

CONSTITUTION: A cover 2 is fixed on one end of an outer cylinder 1, a hole 3 through to the open air is provided on the cover 2, a stem 4 is provided at the center of the outer cylinder 1, and an annular lip valve 5 is provided on an inner periphery of the other end of the outer cylinder 1 inwardly. Then, an adapter 14 having a hole 13 connecting an air valve of a bicycle tyre through to the interior of an inner cylinder 7 is fixed on an outside end of the inner cylinder 9 together with a grip 15.