Molded case circuit breaker

The utility model discloses a molded case circuit breaker, which comprises a base and a moving contact assembly, wherein the base is divided into at least two polar spaces along the width direction of the base by an interphase separation rib; each pole space is internally provided with a partition wall, the partition wall at least divides the pole space into a first cavity and a second cavity, the first cavity is used for placing a static contact, and the second cavity is used for placing a moving contact assembly; a first penetrating channel penetrating through the first cavity and the second cavity is formed in the partition wall, and a first penetrating channel width adjusting assembly detachably fixed to the base is arranged on the partition wall of each pole; when the first through channel width adjusting assembly is not installed, the width of the first through channel is the maximum; after the first through channel width adjusting assembly is installed, the width size of the first through channel is re