FIBER TREATMENT AGENT COMPOSITION

PROBLEM TO BE SOLVED: To provide a fiber treatment agent composition that includes much quaternary ammonium salts containing three ester groups in a molecule and has improved freeze restorability and high temperature stability.SOLUTION: There is provided a fiber treatment agent composition including: 5 to 25 mass% of a cationic surfactant that is quaternary ammonium salts containing ester groups in a molecule (A); 0.01 to 5 mass% of a biguanide compound (B); and 0.1 to 15 mass% of a nonionic surfactant of an ethylene oxide addition type having an EO addition molar number of 35 to 200 (C). The cationic surfactant includes: quaternary ammonium salts containing one ester group in a molecule (A-1); quaternary ammonium salts containing two ester groups in a molecule (A-2); and quaternary ammonium salts containing three ester groups in a molecule (A-3), and the mass ratio of the quaternary ammonium salts containing three ester groups in a molecule (A-3) to the cationic surfactant, ((A-3)/[(A-1)+(A-2)+(A-3)]), is 0.3 to 0.7.