PURPOSE: To apply an ultrathin membrane of a submicron order, by a method wherein air is diffused in a liquid to generate air bubbles which are, in turn, allowed to burst to obtain an aerosol containing ultrafine liquid particles and said aerosol is immediately applied to an object electrostatically.

CONSTITUTION: A liquid thermoplastic resin molten under heating is injected in a hermetically closed container 12 so as to reach a position slightly higher than a jet orifice 14 and held to predetermined temp. by a heater 21. The compressed air CA supplied from the outside is also heated to predetermined temp. to be introduced into an air diffusing pipe 13 and injected in the molten liquid L from the jet orifice 14 to generate air bubbles. These air bubbles rise through the liquid to reach the surface of the liquid, and expand and burst to be scattered into the open air as fragments and an aerosol As containing ultrafine resin particles is formed. This aerosol As is guided to a conduit 16 to be blown off into the open air from the nozzle 8 of an electrostatic gun 17 and corona discharge is generated in the flow of the aerosol As to electrostatically apply ultrafine resin particles to an article A to be coated.