Abstract: A sheet opening/closing apparatus capable of being utilized as any of a sheet spreading mechanism, a ventilating mechanism, and a heat retaining and light shielding mechanism, superior in all of working efficiency, assembling performance and economy, capable of minimizing stain and damage of the sheet used, and exerting no bad influence on the growth of plants. The sheet opening/closing apparatus includes a pair of support rods opposed to each other, a track 8 laid between the two support rods, and a movable member 9 attached to the track 8 movably. By utilizing the movement of the movable member along the track, the sheet is spread or opened between the two support rods.