PURPOSE: To raise a generating efficiency and to lighten an energy burden at the time of lighting a headlamp by connecting the bottom faces of first and second cores constituting a stator by a cylindrical pole core having a large thickness.

CONSTITUTION: The bottom faces 31b, 32b of a first core 31 and a second core 32 are connected by a cylindrical pole core 5 having a large thickness. In the magnetic paths of the bottom face 31b of first core 31 → pole core 5 and the pole core 5 → bottom face 32b of second core 32, a magnetic flux is bent with a relatively large curvature to decrease the loss of magnetic flux in the pole core 5. Also, because said pole core 5 has a large thickness, the magnetic path of said bottom faces 31b, 32b shortens to decrease an iron loss. Further, when said pole core 5 is molded from amorphous metal, magnetic iron powder or high silicon steel, the loss of skin effect in the pole core 5 is decreased still more.