A molded case houses switching parts and includes a case main body and a cover placed on an upper portion of the case main body. The case main body includes a bottom portion case that forms a bottom portion of a circuit breaker and an intermediate case, placed on an upper portion of the bottom portion case, having a dividing wall that blocks off a space between the intermediate case and the bottom portion case. A power source side terminal block and second movable contact are fitted inside the bottom portion case, and a first movable contact, the load side terminal block, the contact portion, and the arc extinguishing chamber are fitted inside the intermediate case.