To ensure the electric connection of a coil to a terminal pin by performing the relative movement of the terminal pin to which an end part of the coil is connected to the molten solder in a solder bath to remove a film of the coil.

A pin 1 of a terminal block 12 of a resolver 10 is immersed in the molten solder 4 of a solder bath 3, and the terminal block 12 or the solder bath 3 is horizontally reciprocated through a relative moving means 20 comprising an actuator. The terminal pin 1 is relatively moved to the molten solder 4, the molten solder 4 is moved to an end part 2a of a coil 2, a film coated on the end part 2a of the coil 2 is peeled or solved through the heat and the movement of the molten solder 4, and the end part 2a whose film is removed is soldered to the terminal pin 1 with the molten solder 4. Thus, the end part 2a of the coil 2 can be completely and electrically connected to the terminal pin 1 after the film is removed.