To provide a rigid plate that can remarkably reduce its weight in comparison with a conventional plate while maintaining required rigidity, and further hardly causes deformation on its surface.

A rigid plate 1 has a structure that comprises: a pair of metal sheets 2 which forms two surfaces 1a respectively; a pair of plastic hollow sheets 3 which is arranged at inner face 2b sides of these metal sheets 2 respectively; and a foam 4 that is arranged between the pair of plastic hollow sheets 3.