PURPOSE: To rapidly and inexpensively form a corrosion resistant film with a predetermined thickness having no pinhole, by supplying a definite amount of a powdery resin into a uniformly heated container, and adhering the resin to the inner surface of the container while successively altering the posture of said container.

CONSTITUTION: A powdery resin is supplied to a pressure feed tank while weighed each time in an amount necessary for forming a film and the total amount thereof is fed into a bomb 1 at once from an access port part 2 through a supply pipe 15 by compressed air from a compressed air pipe. The bomb 1 is uniformly preheated and the supplied powdery resin is fused and adhered to the inner surface of a bottom part by allowing the same to stand still for a predetermined time to form a film with a predetermined thickness. In the next step, the supply pipe 15 is detached while a cap is mounted to the bomb 1 which is, in turn, allowed to stand still for a predetermined time in an inverted state to form a film with a predetermined thickness to the inner surface of the access port part 2. At the last step, the bomb 1 is horizontally placed on a rotary table and a film is formed to the inner surface of a straight tubular barrel part 4 by applying the whole of the residual resin while the bomb 1 is rotated.