Abstract: The air pump is installed on the frame of a bicycle which utilizes the sprocket of the bicycle as the power source. The air pump contains a cylinder member, a transmission member, and a positioning member. The positioning and transmission members are connected to the cylinder member. The positioning member allows the adjustment and positioning of the cylinder member along the bicycle frame so that the cylinder member can be engaged by a front sprocket of the bicycle. The transmission member contains a shaft and a gear. The shaft has one end connected to the cylinder member and another end connected to the gear. When a rider rotates the front sprocket, the rotational power is delivered to the gear and then to the shaft of the transmission member, which in turn drives the cylinder member to pump air for inflation.