To make it possible to repair a roof board slipped from a purlin or rafter, etc., bearing the roof board or having a danger of slipping by only work from the outdoor side of a roof.

A roof board slipping prevention hardware 1 is equipped with a screw bolt 3, wire 4 connected to the lower end side of the screw bolt 3, two main or auxiliary steel plates 8 and 8 and clamping nut 2 screwed in the screw bolt 3. It is inserted in the screw bolt 3 and, at the same time, it is constituted of a cut-off packing 6 and a cap 5 pushed and held to a mounting insertion hole site by the clamping nut 2 in the case of a mounting state.