An adjusting device for automobile headlamp projection angle comprises a case, a bearing ring, a connection beam, a magnet, a main axle, a pair of forward-wound coil and backward-wound coil, a pair of active transmission gear wheel and passive transmission gear wheel, and a circuit board. The circuit board controls the charging of the coils, determining the poiarity of the magnet, whereby the transmission gear wheels will move and drive an up or down shift of the main axle. A stopping piece mounted on the passive transmission gear wheel will move and confine the movement of the main axle between an upper and a lower limits, which limits are controlled by a handle on the circuit board. Therefore, over-extension and over-contraction of the main axle can be prevented. Further, the transmission will be more sensitive, and the total volume of the device will be small.