PURPOSE: To obtain a curable inorganic composition capable of remarkably shortening the curing tame and providing an inorganic cured body having a high strength and excellent in durability.

CONSTITUTION: This curable inorganic composition is obtained by adding 1-300 pts.wt. of a silicic acid alkali metal salt, 1-100 pts.wt. of a boric acid alkali metal salt and 10-1000 pts.wt. water to 100 pts.wt. of one or more kinds of inorganic powder selected from the group comprising (a) fly ash containing ≥80wt.% of powder having ≤20μm particle diameter, (b) fly ash containing ≥80wt.% of powder baked at 400-1000°C and having ≤20μm particle diameter, (c) inorganic powder obtained by melting fly ash or clay and spraying the melt into a gas, (d) inorganic powder obtained by applying clay to a mechanical energy having 0.1-30kwh/kg strengh, (e) inorganic powder obtained by heating inorganic powder of the component (d) at 100-750°C and (f) metakaolin.