The cement admixture and cement composition

A small additive amount showed high dispersibility, provides a particularly high water-reducing ratio cement composition obtained by using the cement admixture and which can exhibit excellent initial dispersibility and dispersion retention even in a region . Wherein two kinds of polymer as an essential component of the A polymer (A) and the polymer (B), and the ratio of the polymer (A) and the polymer (B) (mass%) of 1 a cement admixture which is 99/99 to 1, the polymer (a), the unsaturated (poly) alkylene glycol ether monomer (a) and derived from the structural unit (I) unsaturated monocarboxylic acids system comprising monomer and (b) from the structural unit (II) as essential constituent units, and the structural unit (I) and the structural unit (II) and are each occupies one or more mass% of the total structural units, the proportion of the structural unit (I) is 50 mol% or less polymer in all the structural units, the polymer (B) is a polymer having an oxyalkylene group or a polyoxyalkylene group and a carboxyl group a cement admixture.