A magnetic actuator according to the present invention includes a stator yoke made of a magnetic substance and having projecting streaks on the inner circumference thereof to produce magnetic bias to a rotor magnet. The stator yoke is fitted into and fixed to a coil bobbin, a base plate, or a sheet metal having a concave portion formed therein. This can hold shading members to a totally closed position after shutoff of electric current through a coil and can stably achieve an appropriate position of the stator yoke in a rotation direction to eliminate the need for fixing the stator yoke with an adhesive or the like.