The invention relates to a magneto-optical component, such as a variable light attenuator, light modulator or optical switch, having small size, low power consumption and high speed. The magneto-optical component comprises at least one Faraday rotator comprising a magnetic domain A with magnetization in a direction perpendicular to a light incident/exit surface, a magnetic domain B with magnetization in a direction opposite to the magnetization direction of the magnetic domain A, a planar magnetic domain wall as a boundary between the magnetic domain A and the magnetic domain B, and two light transmission regions through which a plurality of light beams comprising identical traveling directions are transmitted respectively and whose distances from the magnetic domain wall are almost equal to each other, and a magnetic field application system for applying a variable magnetic field to the Faraday rotator to make a position of the magnetic domain wall variable.