An electromagnetic actuator includes a rotor rotatable within a predetermined angular range, a magnetizing coil, and a yoke having an arcuate surface facing the rotor, and first and second magnetic-pole parts that have mutually different magnetic poles upon energizing the coil. The rotor includes a magnetized rotor part defining the outer peripheral surface of the rotor and magnetized to have different magnetic poles, a non-magnetized driving pin rotatable with the magnetized rotor part, and a protrusion part protruding radially from the rotor and facing the first or second magnetic-pole part while being magnetized to have the same magnetic pole as the outer peripheral surface of the rotor. The surface of the rotor that faces the yoke and that exerts a magnetic action is increased due to the inclusion of the protrusion part, and hence a desired maintaining force and driving torque can be obtained.