A molded case circuit breaker, comprising: a case; a power side terminal portion and a load side terminal portion formed at two sides of the case; a mounter installed at the terminal portion with a structure to enclose a terminal connector connected to the terminal portion, wherein the mounter includes: a mounting surface for mounting the terminal connector; insulation surfaces extending from two side edges of the mounting surface, and spaced from each other; and a cover surface having an opening, and formed on outer side surfaces of the insulation surfaces so as to cross the insulation surfaces and the mounting surface, wherein the mounter includes a shielding unit extending from the mounting surface toward a rear surface of the case, and configured to obtain a phase-to-ground insulation distance, wherein the shielding unit includes: mounting surface connection portions extending toward a bottom surface of the case from a bottom surface of the mounting surface, and spaced from each other in a side direction of the case; and a supporting portion connecting end portions of the mounting surface connection portions thereto, the molded case circuit breaker being characterized in that: the mounter is provided with an insulation distance extension portion extending from the cover surface in parallel to the insulation surface, the insulation distance extension portion is interposed between terminal connectors which are spaced from each other in a side direction of the case to prevent a short-circuit between phases due to arc gas, the mounting surface is provided with a separation prevention member which protrudes from one end the of the mounting surface toward an inner portion of the power side and load side terminal portions to prevent the terminal connector from being separated from the mounting surface, the separation prevention member is provided with a locking protrusion at an end thereof, and is elastically supported at the mounting surface, and one side of the terminal connector is fixed to the mounting surface by being locked by the locking protrusion. a case; a power side terminal portion and a load side terminal portion formed at two sides of the case; a mounter installed at the terminal portion with a structure to enclose a terminal connector connected to the terminal portion, wherein the mounter includes: a mounting surface for mounting the terminal connector; insulation surfaces extending from two side edges of the mounting surface, and spaced from each other; and a cover surface having an opening, and formed on outer side surfaces of the insulation surfaces so as to cross the insulation surfaces and the mounting surface, a mounting surface for mounting the terminal connector; insulation surfaces extending from two side edges of the mounting surface, and spaced from each other; and a cover surface having an opening, and formed on outer side surfaces of the insulation surfaces so as to cross the insulation surfaces and the mounting surface, wherein the mounter includes a shielding unit extending from the mounting surface toward a rear surface of the case, and configured to obtain a phase-to-ground insulation distance, wherein the shielding unit includes: mounting surface connection portions extending toward a bottom surface of the case from a bottom surface of the mounting surface, and spaced from each other in a side direction of the case; and a supporting portion connecting end portions of the mounting surface connection portions thereto, mounting surface connection portions extending toward a bottom surface of the case from a bottom surface of the mounting surface, and spaced from each other in a side direction of the case; and a supporting portion connecting end portions of the mounting surface connection portions thereto, the molded case circuit breaker being characterized in that: the mounter is provided with an insulation distance extension portion extending from the cover surface in parallel to the insulation surface, the insulation distance extension portion is interposed between terminal connectors which are spaced from each other in a side direction of the case to prevent a short-circuit between phases due to arc gas, the mounting surface is provided with a separation prevention member which protrudes from one end the of the mounting surface toward an inner portion of the power side and load side terminal portions to prevent the terminal connector from being separated from the mounting surface, the separation prevention member is provided with a locking protrusion at an end thereof, and is elastically supported at the mounting surface, and one side of the terminal connector is fixed to the mounting surface by being locked by the locking protrusion. the mounter is provided with an insulation distance extension portion extending from the cover surface in parallel to the insulation surface, the insulation distance extension portion is interposed between terminal connectors which are spaced from each other in a side direction of the case to prevent a short-circuit between phases due to arc gas, the mounting surface is provided with a separation prevention member which protrudes from one end the of the mounting surface toward an inner portion of the power side and load side terminal portions to prevent the terminal connector from being separated from the mounting surface, the separation prevention member is provided with a locking protrusion at an end thereof, and is elastically supported at the mounting surface, and one side of the terminal connector is fixed to the mounting surface by being locked by the locking protrusion.