Disclosed are the following: a cement dispersant which is excellent in initial dispersibility and further in flow retainability of cement, because of using a polymer having a proper molecular weight distribution; a process for producing this cement dispersant; and a cement composition using this cement dispersant. The cement dispersant comprises a water-soluble polymer (P) as a main component, and is characterized by displaying an area proportion (a value (A-B) given by subtracting an area ratio B of a lower molecular weight side portion from an area ratio A of a higher molecular weight side portion) in the range of 13 to 60%.