To prevent the shining-in of light at the time of opening and closing by arranging a moving floor towards an interior from the front of an entrance and disposing a flexible sheet curved in a corrugated shape being oscillated in the horizontal direction and generating a forward wave motion towards the other end from one end.

Rollers 26, 27 are fixed on the insides of shafts 11, 12, and a conveyor 28 is hung. Cylindrical cams 36, 37, 38 are fastened on the insides of shafts 29, 30, 31, and upwards opened channel bars are arranged in parallel with the lower sides of the shafts 29, 30, 31 respectively. Disks are inserted into each channel bar, slide runners are protruded from the top faces of the disks and inserted into thread grooves 42, the upper edges of flexible sheets 47 are fixed to lower sections, and lower edges are hung up so as to be brought near to the conveyor 28. When a motor 18 is rotated, the conveyor 28 is tuned, the disks are reciprocated in the channel bars 39, 40, 41 by the thread grooves 42, both end sections and an intermediate section are rectilinearly propagated in the amplitude direction in the flexible sheet 47, and a forward wave motion is generated. Accordingly, the shining-in of light from the outside can be prevented.