A vacuum circuit breaker (1A; 1B), comprising: a cylindrical grounded tank in which an insulating gas is sealed; a vacuum valve insulated and supported in the grounded tank, the vacuum valve including a movable-side contact and a fixed-side contact; a movable-side electrode electrically connected to the movable-side contact; a fixed-side electrode electrically connected to the fixed-side contact; a movable-side bushing extending above the grounded tank; a fixed-side bushing extending above the grounded tank; a movable-side frame electrically connecting a lower end of the movable-side bushing to the movable-side electrode; a fixed-side frame electrically connecting a lower end of the fixed-side bushing to the fixed-side electrode; an insulated operating rod to move the movable-side electrode; a movable-side insulator insulating and supporting the movable-side frame in the grounded tank; a fixed-side insulator insulating and supporting the fixed-side frame in the grounded tank; a movable-side flange covering a movable-side end portion of the grounded tank; a fixed-side flange covering a fixed-side end portion of the grounded tank; a bellows disposed in the vacuum valve, the bellows allowing the movable-side electrode to pass through and being fixed to the movable-side electrode, to expand and contract with movement of the movable-side electrode; characterized by a pressure valve (41; 43) configured to regulate pressure of the insulating gas between a first area enclosed by the bellows, the movable-side frame, the movable-side insulator, and the movable-side flange and a second area enclosed by the grounded tank, the movable-side flange, and the fixed-side flange outside the first area; a pressure release valve configured to release the insulating gas from the first area to an outside of the grounded tank; a pressure sensor configured to measure a gas pressure in the second area; and an anomaly determination unit configured to determine whether or not the insulating gas has leaked from the grounded tank, based on the gas pressure measured by the pressure sensor, wherein a first gas pressure that is a gas pressure in the first area is lower than a second gas pressure that is the gas pressure in the second area, the pressure valve (41; 43) being configured to open when a first pressure difference obtained by subtracting the first gas pressure from the second gas pressure exceeds a first specific value, and the pressure release valve being configured to open when a second pressure difference obtained by subtracting a pressure outside the grounded tank from the first gas pressure exceeds a second specific value. a cylindrical grounded tank in which an insulating gas is sealed; a vacuum valve insulated and supported in the grounded tank, the vacuum valve including a movable-side contact and a fixed-side contact; a movable-side electrode electrically connected to the movable-side contact; a fixed-side electrode electrically connected to the fixed-side contact; a movable-side bushing extending above the grounded tank; a fixed-side bushing extending above the grounded tank; a movable-side frame electrically connecting a lower end of the movable-side bushing to the movable-side electrode; a fixed-side frame electrically connecting a lower end of the fixed-side bushing to the fixed-side electrode; an insulated operating rod to move the movable-side electrode; a movable-side insulator insulating and supporting the movable-side frame in the grounded tank; a fixed-side insulator insulating and supporting the fixed-side frame in the grounded tank; a movable-side flange covering a movable-side end portion of the grounded tank; a fixed-side flange covering a fixed-side end portion of the grounded tank; a bellows disposed in the vacuum valve, the bellows allowing the movable-side electrode to pass through and being fixed to the movable-side electrode, to expand and contract with movement of the movable-side electrode; characterized by a pressure valve (41; 43) configured to regulate pressure of the insulating gas between a first area enclosed by the bellows, the movable-side frame, the movable-side insulator, and the movable-side flange and a second area enclosed by the grounded tank, the movable-side flange, and the fixed-side flange outside the first area; a pressure release valve configured to release the insulating gas from the first area to an outside of the grounded tank; a pressure sensor configured to measure a gas pressure in the second area; and an anomaly determination unit configured to determine whether or not the insulating gas has leaked from the grounded tank, based on the gas pressure measured by the pressure sensor, wherein a first gas pressure that is a gas pressure in the first area is lower than a second gas pressure that is the gas pressure in the second area, the pressure valve (41; 43) being configured to open when a first pressure difference obtained by subtracting the first gas pressure from the second gas pressure exceeds a first specific value, and the pressure release valve being configured to open when a second pressure difference obtained by subtracting a pressure outside the grounded tank from the first gas pressure exceeds a second specific value.