PURPOSE: To obtain a reinforcing material for hydraulic inorganic molded article capable of providing a hydraulic inorganic composition having excellent moldability without generating an undissolved lump of powder even with a small amount of water and to produce a high-strength inorganic hardened material.

CONSTITUTION: Substantially, the whole surface of a highly water absorbing resin having absorbed water is coated with powder of flat inorganic substance having a smaller particle diameter than that of the highly water absorbing resin to give a reinforcing material for hydraulic inorganic molded article. The reinforcing material for hydraulic inorganic molded article is mixed with a hydraulic inorganic substance to give a mixture, which is extrusion molded to give a hydraulic inorganic molded article and the molded article is hardened.