PURPOSE: To make forming easy and to obtain high performance and high reliability by making a plastic sealed coil with a thermoplastic plastic which contains an electrically insulated oil for the electrically insulating plastic of an external insulating part.

CONSTITUTION: A plastic sealed coil 1A is formed by winding a coil 3 on a coil bobbin 2 and by integrally fixing and sealing the coil bobbin 2 and the coil 3 with the external insulating part 4A of a polyacetal resin forming material, an electrically insulating plastic thermoplastic resin forming material, containing an electrically insulating mineral oil. If a gap 6 is made among coil conductors 3A due to the insufficient filling of the thermoplastic resin forming material, the contained electrically insulating oil moves in the gap 6 and the surfaces of the coil conductors 3A are coated or the gap 6 is filled with the oil.