PURPOSE: To obtain a sealed magnetic torque transmitting device by air-tightly tightening a housing of a stator iron core fitted to a casing, and applying an anticorrosion member to a gap and the periphery between both the iron cores exposed in gas in a closed vessel of the housing to prevent rust.

CONSTITUTION: A vessel, constituted of a rotor iron core 13 integrally formed with a shaft 10 of a fan 6 and a housing 15 of inserting a stator iron core 14 and actually sealed with gas 17, is fixed to a casing 21 by screws 22 so as to generate a flow of gas by turning the fan 6 in the vessel. When an AC power supply is applied to the stator iron core 14, the rotor iron core 13 is actuated as an induction motor to rotate. The stator iron core 14 is protected by providing an anticorrosion member 16 of Ni plate or the like between the rotor and stator iron cores 13, 14 against infiltration of the gas 17 into the housing 15 through a bearing 11.