To simply and inexpensively fit a film member.

At the periphery of the film member 3, an engaging member 3 fitted so as to tuck up an inner end is provided. A frame body (engaging frame) 4 to be fitted to this film member 2 is provided with an engaging groove 5 which has a receiving part 6a on which an end part 3a inside of the engaging member 3 pulled by inward tension applied to the film member is abutted and a hook part 6b which is abutted on the fixed end part 3b of the periphery of the film member 2 to prevent the engaging member 3 from rotation expanding outward and which is provided with an engaging member insertion port 6c opening in a direction opposite to the tensioning direction of the film member 2. In the state of tensioning the film member 2, the engaging member 3 is inserted to the engaging groove 5 and hooked to the receiving part 6a and the hook part 6b to fit the film member 2 to a frame body (engaging frame) 4.