To perform easy and safe removal of a protective sheet by attracting both end edges of the protective sheet for covering at least the upper surface and both side surfaces of a truss to the lower ends of the side surfaces of the truss.

This curing device 4 for curing an entire truss 1 comprises a plurality of protective sheets (5-8), a plurality of attracting means 9 made of magnets such as magnet sheets respectively mounted to both end edges of these protective sheets 5-8, string-like pulling means 10 for removing these attracting means 9. The interconnection between the protective sheets 5-8 is provided by joint to a Velcro(R) body mounted to the upper surface of the protective sheet 5, for example, so that the plurality of protective sheets 5-8 can be arbitrarily separated from and connected to each other. When the pulling means 10 are pulled upward of a truss 1, the attracting means 9 separate from the lower ends of the side surfaces of the truss 1 to easily remove the protective sheets 5-8.