A switching operation mechanism to a molded case circuit breaker, including at least one operating handle, which is movable in a rotatable trajectory, said switching operation mechanism including at least one external rotary handle, at least one operation member and at least one movement transmission means, the said operation member being capable of moving in rotating trajectory in equivalent direction to the movement in rotating trajectory of the handle for operating the circuit breaker in molded case, arranged inside a housing including a laterally bipartite body, reaching an efficient movement transfer, requiring less mechanical effort of proportional operation of the user on the external rotary handle, wherein it is possible to maintain an external rotary handle, of great dimensions proportional to the assembled assembly, “within” the general perimeter of the molded case circuit breaker.