PURPOSE: To contrive improvement in setting hardenability, by blending α-type calcium tertiary phosphate with calcium secondary phosphate hydrate at a specific molar ratio of Ca/P.

CONSTITUTION: A change of α-type calcium tertiary phosphate Ca3(PO4)2 into apatite and octacalcium phosphate (OCP) is advanced within a weak acidic range in water. On the other hand, a change of calcium secondary phosphate dihydrate (CaHPO4.2H2O) into the apatatite and OCP is similarly advanced within a weak acidic to basic range in water. The α-type calcium tertiary phosphate is blended with calcium secondary phosphate dihydrate at 1.20W1.47 molar ratio of Ca/P to form a blended powder, which is then kneaded with water and kept. In the process, since the pH condition required for hydrating reaction of both mutually complements, advance of the hydrating reaction is accelerated. Thereby setting hardenability of a hydraulic cement composition is improved.