To prevent foreign matters from sticking when an electric current is broken, by providing a trip mechanism part for tripping a movable piece, and a rotation shaft for transmitting the movement of this mechanism part to the movable piece, in the same casing.

At the time of normal electrification, a handle 14 is in a closed circuit position, to join a movable piece 6 and a fixed piece 5. When an abnormal electric current is generated in a circuit in this condition, this is detected by a detecting part 2, to drive a trip mechanism part 3. The trip action of the trip mechanism 3 is converted into rotating force, for rotating a rotation shaft 20 by a connecting arm 22. When the rotation shaft 20 is rotated, this rotation is transmitted to a bevel gear, attached to a movable piece turning shaft 21, to turn the movable piece 6 in a contact-parting direction to part a contact, thereby breaking the abnormal electric current. By this constitution, the distance, between the trip mechanism 3 and an arc extinguishing chamber 4 wherein an arc is generated, can be ensured, thereby preventing foreign matters from sticking to the trip mechanism part 3.