PURPOSE: To provide a thin plate stone material excellent in acid resistance, earthquake resistance, impact resistance and heat resistance, reduced in wt. as a whole and easily formed into a complicated shape by combining a thin stone material with urethane foam to which strength is applied to a reinforcing plate from a such a notion that a stone is heavy.

CONSTITUTION: Reinforcing plates 3, 3a are bonded to a thin stone material 1 to be combined with a separate reinforcing plate or solid and, after the outer periphery of the combined structure is arranged, the space of the combined structure is filled with an urethane foaming agent to fix the whole.