A novel cement is alkalescent, capable of solidifying a wide range of soil and applicable to biological environment. The cement composition contains 100 parts by weight of magnesium oxide, 5 to 25% by weight of at least one of silicic acid, alumina and iron oxide, 3 to 35 parts by weight of a phosphate, 2 to 30 parts by weight of gypsum and 0.005 to 7 parts by weight of a hydroxycarboxylic acid or a ketocarboxylic acid.