metal principal surface 22 then as with the first film forming step mentioned above the film forming chamber 51 is sealingly closed and depressurized by a vacuum pump not shown to 10 2 pa furthermore the second mixed microparticles d 2 are supplied on the inside bottom plate 58 r of the aerosol generator 58 and then the opening of the container 58 p is closed with the stopper 58 q as with the first film forming step subsequently the regulator 59 placed at some point in the gas pipe p 1 is controlled to flow a predetermined flow rate of carrier gas not shown from the gas bomb gb this carrier gas will flow in the aerosol generator 58 through the gas pipe p 1 accordingly this carrier gas causes the second mixed microparticles d 2 to be raised or stirred up in a space between the inside bottom plate 58 r and the stopper 58 q thereby producing the second aerosol as 2 thus the second mixed microparticles d 2 of a predetermined carrying quantity per unit time which is determined by the flow rate of carrier gas are carried by the carrier gas the thus produced second aerosol as 2 is delivered to the injection nozzle 52 of the film forming chamber 51 through the aerosol pipe p 2 as with the first film forming step the second aerosol as 2 delivered to the injection nozzle 52 is further accelerated through the tapered injection part 52 h and injected to the second film forming surface 22 c of the second metal principal surface 22 of the metal foil 20 thus the second mixed microparticles d 2 collide with and are deposited on the second metal principal surface 22.