PURPOSE: To deal with a complex shape of a ring-like support member for an armature coil and concurrently improve a heat dissipating quality of the ring-like support member, by applying an insulating bonding agent to the required part of the conductive ring-like support member for the armature coil, which supports the end part of the armature coil of a rotating machine, and by electro-depositing a mica powder on the conductive ring-like support member, and thereafter, by forming an insulating film on the required part through curing the insulating bonding agent.

CONSTITUTION: An insulating bonding agent such as a molten epoxy resin is applied to the insulation requiring part of a metallic support member 8, and thereby, a film 9 is formed. The metallic support member 8 is inserted into a space 7, and it is grounded. Further, by applying a DC high voltage in a predetermined time to a bottom plate 5 of a mica storing part 1 and to a sidewall 6, an electrostatic field is formed between the support member 8 and the bottom plate 5 plus the sidewall 6. By vibrating the mica storing part 1 in the predetermined time through a vibrator, a mica power 4 charged positively is made to fall into the space 7 via the bottom plate 5 made of a metallic mesh. Then, by the electrostatic field, the mica powder 4 is stuck attractively on the support member 8. After taking out the support member 8 from the foregoing apparatus, the mica powder 4 stuck on the part of the support member 8, whereto no bonding agent is applied, is removed by giving a vibration to the support member 8. Thereafter, the bonding agent is heated and it is cured. Thereby, an insulating film 11 is formed completely on the support member 8.