To provide a composition for cement mortar where the usable time of produced cement mortar is long, where the separation resistance in water of the cement mortar is excellent and where the bending strength and the bending toughness of molded concrete are high.

The composition for cement mortar containing quick curing cement, mineral fine powders, a fine aggregate, a high performance water reducer, a fiber material and a separation resistant agent in water is characterized by blending the mineral fine powders of 10-30 pts.mass, the fine aggregate of 50-150 pts.mass, the high performance water reducer of 0.2-0.3 pts.mass, the fiber material of 0.1-1.0 pts.mass and the separation resistant agent in water of 0.01-1.0 pts.mass based on 100 pts.mass of the quick curing cement and by a fineness of the mineral fine powders of 4,000 cm2/g or more.