To prevent the disturbance of a spray pattern of a coating material using a protective sheet laminated on the inner surface wall of a coating booth to rebound electrically charged coating material particles to prevent the deposition of coating material particles on the inner surface.

The protective sheet 12 is structured so as to adhere a thin film sheet 12a and a thin film sheet 12b having a plurality of air cap part B to each other and a plurality of gas layers A isolated from the outside are formed inside. The protective sheet 12 formed in this way is laminated so that the thin film sheet 12a faces the inside of a coating chamber 8 and the air cap parts B of the thin film 12b are brought into contact with the inner wall surface 8a of the coating chamber 8 at a plurality of contact points D. When the charged coating material particles are sprayed in the coating camber 8, air in the gas layers A and air in the gas layer A' are charged to rebound the coating material particles, but because the protective film 12 itself is not charged to weaken the rebounding force and as a result, the spray pattern of the coating material is not disturbed.