To provide a circuit breaker which performs neither reset operation not latch when a fixed contact point and a movable contact point are welded together.

A circuit breaker includes: a trip arm 6 locked at a latch piece 7, which is deformable with overcurrent or the like, to keep a closed state of a contact point; and a toggle link unit 4 having an upper toggle link 4a and a lower toggle link 4b. The end of the upper toggle link 4a is coupled with the trip arm 6 and the end of the lower toggle link 4b is coupled with a movable contact 2. When the latch piece 7 has deformed, the locking between the latch piece 7 and the trip arm 6 is released, thereby causing a trip operation, and in turn the toggle link unit 4 performs opening operation on the movable contact 2. After a trip operation occurs with a movable contact point 2a and a fixed contact point 3a welded together, if an operating handle 1 performs off operation, an engagement protrusion 19 in contact with a bracket 8 supporting the operating handle 1 appears at the upper toggle link 4a, thereby suppressing rotary movement of the trip arm 6 to prevent from being locked at the latch piece 7.