To provide a novel laterally roofing long roof plate extremely suitable for resolving various problems and requiring no pasted caulking agent.

A laterally roofing long roof plate with a snowfall preventing protrusion used for laterally roofing on a roof plane of a building has a U-shaped upper contacted portion 2 open downward and formed on the upper side of a laterally roofing long roof plate mainbody 3 by bending the same and a U-shaped lower contacted portion 1 open upward and formed on the lower side of the laterally roofing long roof plate mainbody 3 by bending the same and an elastic string waterproof packing 15 inserted in the upper contacted portion or the lower contacted portion 1 in a slip off falling impossible manner.