A circuit breaker (101, 102) comprising: a housing; a movable contact member (9, 28) that has a moving contact point (8, 10) on at least one end; a stationary contact member (6, 12, 27) that has a stationary contact point (11, 7) contacting with or separating from the moving contact point (8, 10); a holding member for holding the movable contact member (9, 28); and a make and break mechanism that comprises: a lower link for driving the holding member; a lever that is engaged with a latch of an over-current tripping device, the lever revolving at the time of tripping the circuit breaker (101, 102); an upper link that is supported on the lever, the upper link coupled with the lower link via a spring pin, the upper link making up a toggle link together with the lower link; a main spring that is coupled with the spring pin on a driven side of the main spring; and a handle arm, the handle arm coupled with the main spring on a driving side of the main spring, wherein the housing is configured to comprise a double-break unit case having two pairs of the moving contact point (8, 10) and the stationary contact point (11, 7) or configured to comprise a member that forms a structure having one pair of the moving contact point and the stationary contact point, characterized in that it comprises a frame that is fixed to the housing, the frame having a first fixing portion for fixing the make and break mechanism to the double-break unit case and a second fixing portion for fixing the make and break mechanism to the housing in which the member is stored, wherein the handle arm has a substantially U-character shape and wherein the handle arm is rotatably supported on the frame. a housing; a movable contact member (9, 28) that has a moving contact point (8, 10) on at least one end; a stationary contact member (6, 12, 27) that has a stationary contact point (11, 7) contacting with or separating from the moving contact point (8, 10); a holding member for holding the movable contact member (9, 28); and a make and break mechanism that comprises: a lower link for driving the holding member; a lever that is engaged with a latch of an over-current tripping device, the lever revolving at the time of tripping the circuit breaker (101, 102); an upper link that is supported on the lever, the upper link coupled with the lower link via a spring pin, the upper link making up a toggle link together with the lower link; a main spring that is coupled with the spring pin on a driven side of the main spring; and a handle arm, the handle arm coupled with the main spring on a driving side of the main spring, a lower link for driving the holding member; a lever that is engaged with a latch of an over-current tripping device, the lever revolving at the time of tripping the circuit breaker (101, 102); an upper link that is supported on the lever, the upper link coupled with the lower link via a spring pin, the upper link making up a toggle link together with the lower link; a main spring that is coupled with the spring pin on a driven side of the main spring; and a handle arm, the handle arm coupled with the main spring on a driving side of the main spring, wherein the housing is configured to comprise a double-break unit case having two pairs of the moving contact point (8, 10) and the stationary contact point (11, 7) or configured to comprise a member that forms a structure having one pair of the moving contact point and the stationary contact point, characterized in that it comprises a frame that is fixed to the housing, the frame having a first fixing portion for fixing the make and break mechanism to the double-break unit case and a second fixing portion for fixing the make and break mechanism to the housing in which the member is stored, wherein the handle arm has a substantially U-character shape and wherein the handle arm is rotatably supported on the frame.