To surely shield light between a slide and a pack main body.

A V-shaped groove 22 is formed on the surface in slide contact with the slide 5 of the back main body 3 so that the groove 22 may be vertical to the moving direction of the slide 5. On the inclined plane 22a on the opening side of the groove 22, one edge part 25a of a plush member 25 is firmly fixed through the base 24a of an elastic plate 24 so that the other edge part 25b may project outside the groove 22. The elastic plate 24 is bent at a bending line 24b so that the leading end part 24c may be erected and the edge part 25b of the plush member 25 may be pressed against the slide 5. Thus, even in the case the gap between the slide 5 and the pack main body 3 becomes larger due to the distortion of the slide 5 in operation, the edge part 25b of the plush member 25 is pressed against the slide 5 by the leading end part 24c of the elastic plate 24, so that external light is prevented from entering the film housing chamber.