To provide a sealing device capable of sealing an inner peripheral face and an outer peripheral face at the same time.

The sealing device has an outside sealing device 10 arranged on the outer peripheral side of a coil 2, and an inner sealing device 20 inserted into an inner hole of the coil 2. Air is supplied to air chambers 14 and 26 of the outside sealing device 10 and the inside sealing device 20, rubbers 12 and 22 are expanded, the rubber 12 is closely adhered to the outer peripheral face of a core 2, and the rubber 22 is closely adhered to the inner peripheral face of the core 2. In this state, the core 2 is impregnated with a resin R from a nozzle 6, and the resin R is cured by heat treatment. After the impregnation of the core 2 with the resin R is completed, the sealing device is turned up-side-down, and the core 3 is also impregnated with the resin R in the same way.