Abstract: A circuit breaker has a body providing a lever pivotally mounted on the upper end thereof. Two terminals are disposed within the body, wherein the first terminal forms a bimetal thereon. The terminals are electrically connected with each other in a normal state. A linkage is mounted on an end of the lever, which forms an isolated member on the lower end of the linkage. Pressing the lever, the isolated member of the linkage will moved upwards to separate the two terminals. When the lever is held by some heavy substances, the bimetal can be deformed to disconnect with the second terminal in over-current for cutting out the circuit.