PURPOSE: To prepare a metal sprayed substrate having an insulating layer excellent in piezo-electric characteristics inexpensively in good efficiency, by simultaneously metal spraying an inorg. insulating material and an org. insulating material with respect to the surface of a substrate respectively by a metal spray gun and a spray gun.

CONSTITUTION: A metal pray gun 31 for injecting an alumina particle 21 being an inorg. insulating material and a spray gun 32 for injecting an org. insulating material 22 are provided in parallel relationship above a substrate 11 to simultaneously inject the alumina particle 21 and the org. insulating material 22 onto the substrate 11. Heat being sprayed from the above mentioned metal spray gun 31 is utilized in curing the org. insulating material 22. By this method, an insulting layer 12 wherein the alumina particle 21 is mixed in the org. insulating 22 is formed on the surface of the substrate 11 to obtain a metal sprayed substrate of which dielectric strength is enhanced to a large extent.