Abstract: A circuit protector for protecting a circuit from an overcurrent including a U-shaped main yoke, a main permanent magnet arranged between legs of the U-shaped yoke, a main coil wound around the main yoke, a movable member made of magnetic material and arranged at an open end of the U-shaped yoke, a magnetic device for generating a magnetic force for moving the movable member in a direction away from the yoke, a movable contact secured to the movable member and a fixed contact provided in opposition to the movable. The coil and the movable and fixed contacts are connected in series with a circuit to be protected across a D.C. power supply source. When an overcurrent flows through the coil, the coil generates a magnetic flux having an opposite direction to that of a magnetic flux induced by the permanent magnet, so that a magnetic force for attracting the movable member to the yoke is decreased.