An improved structure of a circuit breaker is provided which comprises a housing, a rocker-switch, a push-shaft, a pull-shaft, a bimetallic strip, and other parts. There are three terminals under the rocker-switch inside the housing. A bimetallic strip embedded in a groove under the pull-shaft makes contact with that pull-shaft through a silver point at one end. The bimetallic strip also makes contact with the push-shaft at the other end using another silver point. Both the pull-shaft and the push-shaft are connected with a curved spring installed inside the V-shaped slot on an adjustment strip. The bimetallic strip, curved spring, and both the pull-shaft and the push-shaft constitute the main control mechanism that provides the circuit breaking action under overloading condition.