Abstract: A gas insulated electromagnetic induction appliance in which a non-condensing insulating gas and a condensing insulating coolant are confined, comprises (a) a pressure detector for detecting a pressure within the container vessel; (b) a gas reservoir connected to the container vessel through a gas discharging passageway including a pipe line, a first gas valve, a compressor, and a gas diffuser; a gas feeding passageway including a pipe line and a second gas valve; and a liquid feeding passageway including a pipe line and a liquid valve; (c) a definite quantity of insulating coolant confined in the gas reservoir; (d) a liquid surface detector for detecting a quantity of the insulating coolant in the gas reservoir; and (e) control means which controls the gas valve, the liquid valve, and the compressor to thereby regulate a pressure in the container vessel and a quantity of the liquid in the gas reservoir.