The present invention provides a cement slurry composition, containing a hydraulic cement material, (A) a first water-soluble low molecular weight compound and (B) a second water-soluble low molecular weight compound differing from the compound (A), wherein a combination of the compounds (A) and (B) is (I) the compound (A) selected from cationic surfactants and the compound (B) selected from anionic aromatic compounds; or (II) the compound (A) selected from cationic surfactants and the compound (B) selected from brominated compounds, and in the compound (A), a ratio of compounds having a hydrocarbon group of 18 or more carbon atoms is not less than 45% by weight.