A vacuum circuit breaker comprising: - a main circuit structure body including a vacuum switch having a fixed contact and a movable contact, a fixed side terminal connected to the fixed contact of the vacuum switch, a movable side terminal connected to the movable contact of the vacuum switch, and an insulation rod coupled to the movable contact of the vacuum switch, the insulation rod opening and closing the fixed contact and the movable contact; and - an insulating holder for supporting the main circuit structure body, - wherein the insulating holder is a frame structure body having opening portions (5a, 5b, 5c, 5d) in top and bottom surfaces and both side surfaces of a section in which the vacuum switch is disposed and a section in which the insulation rod is disposed, - the frame structure body includes two U-shaped frames stacked, insulating holder fixation portions integrally and vertically connecting one ends of the two stacked U-shaped frames close to the opening portions (5a, 5b) of the frame structure body, and intermediate frames coupling intermediate portions of the U-shaped frames, and - wherein the frame structure body includes one end of an upper frame, which is the upper one of the U-shaped frames, and one end of a lower frame, which is the lower one of the U-shaped frames, on the opening side, are integrally coupled by the insulating holder fixation portion extending vertically, and the intermediate portions of the U-shaped upper frame and lower frame are coupled integrally by the intermediate frames extending vertically, - the insulation rod is disposed in a space surrounded by the insulating holder fixation portions, the intermediate frames, and parts of the U-shaped frames close to the insulating holder fixation portions, and - the vacuum switch is disposed in a space surrounded by corners of the U-shaped frames and the intermediate frames. - a main circuit structure body including a vacuum switch having a fixed contact and a movable contact, a fixed side terminal connected to the fixed contact of the vacuum switch, a movable side terminal connected to the movable contact of the vacuum switch, and an insulation rod coupled to the movable contact of the vacuum switch, the insulation rod opening and closing the fixed contact and the movable contact; and - an insulating holder for supporting the main circuit structure body, - wherein the insulating holder is a frame structure body having opening portions (5a, 5b, 5c, 5d) in top and bottom surfaces and both side surfaces of a section in which the vacuum switch is disposed and a section in which the insulation rod is disposed, - the frame structure body includes two U-shaped frames stacked, insulating holder fixation portions integrally and vertically connecting one ends of the two stacked U-shaped frames close to the opening portions (5a, 5b) of the frame structure body, and intermediate frames coupling intermediate portions of the U-shaped frames, and - wherein the frame structure body includes one end of an upper frame, which is the upper one of the U-shaped frames, and one end of a lower frame, which is the lower one of the U-shaped frames, on the opening side, are integrally coupled by the insulating holder fixation portion extending vertically, and the intermediate portions of the U-shaped upper frame and lower frame are coupled integrally by the intermediate frames extending vertically, - the insulation rod is disposed in a space surrounded by the insulating holder fixation portions, the intermediate frames, and parts of the U-shaped frames close to the insulating holder fixation portions, and - the vacuum switch is disposed in a space surrounded by corners of the U-shaped frames and the intermediate frames.