PURPOSE: To surely impede operation of manually opening/closing and operation of automatically opening/closing by an electric motor drive, a gas-blast-load- brake switch, when a pressure of insulating gas in a case is decreased to a specified value or less.

CONSTITUTION: When a pressure of insulating gas in a case is decreased to a specified value or less, a manual operation handle lock device and an automatic opening lock device, comprising an automatic opening means formed of a solenoid 68 and a latch lever 73, are connected cooperatively movably, and a movable electrode open/close operating device is drive-connected to the automatic opening lock device through a lock mechanism opening lever 70 and a lock mechanism holding plate 86. When a pressure of the insulating gas is decreased to the specified value or less, in the case of wrongly closing the current carrying circuit, automatically opening a movable electrode, by actuating the movable electrode open/close operating device, by operating the automatic opening means, is surely impeded by the automatic opening lock device.