The purpose of the present invention is to provide: a copolymer for cosmetics, which has excellent water repellency and oil repellency even though a polyfluoroalkyl group therein has 6 or less carbon atoms； a surface treatment agent which contains the copolymer for cosmetics； a powder for cosmetics, which is treated with the surface treatment agent and has excellent water repellency and oil repellency； and a cosmetic preparation which contains the powder for cosmetics. A copolymer for cosmetics of the present invention contains: 70-90% by mass of a constituent unit (A) that is derived from a compound represented by formula (a)； 2-25% by mass of a constituent unit (B) that is derived from a compound represented by formula (b)； 2-25% by mass of a constituent unit (C) that is derived from a compound represented by formula (c)； 0.1-10% by mass of a constituent unit (D) that is derived from a compound represented by formula (d)； and a residue (E) of a chain-transfer agent (e) that contains an OH group or a COOH group.CH2═CR1—COO-Q1-Rf (a)CH2═CR2-Q2-COOH (b)CH2═CR3—COO—(R4O)n-R5 (c)CH2═CR7—COO-Q3-P(O)(OH)—R8 (d)
