To provide a production process for inorganic plates that can give inorganic plates having a variety of excellent properties without reduction in productivity.

When an inorganic plate is produced by subjecting a cement material containing cement, siliceous materials and fiber components as solid component to autoclave curing, the scrap material that is prepared by grinding the defective products of the inorganic plates is admixed thereto in an amount of 10-20 wt.% of the solid basis. Even when the autoclave maturity is not increased, the reactivity of the siliceous material is raised thereby increasing the formation of tobermorite.