A circuit breaker comprises a fixed contact, which conductively accesses a power or load side of a power circuit; a movable contact, which is selectively contacted with the fixed contact and is located at an off position to make the power circuit become a close circuit, or is separated from the fixed contact and is located at an on position to make the power circuit become an open circuit; a rotating shaft, which rotates along with the movable contact; a handle, which provides a driving force for moving the movable contact; a handle shaft part, which rotatably supports the handle; a handle connecting rod, which transmits the driving force of the handle to the rotating shaft; and a quick insertion rod, which is coaxially combined with the handle shaft part. The quick insertion rod comprises a first guide part and a second guide part, wherein the first guide part has a contact surface that is contacted with the handle connecting rod, and the second guide part has a non-contact surface that is not contacted with the handle connecting rod. In addition, the length (L1) of the contact surface is designed to be shorter than the length (L2) of the non-contact surface.