This hair shaping agent contains (A) a compound represented by formula (1), and (B) water. (In formula (1), R1, R2, and R3 represent H or a group represented by formula (2) thereamong, 0 to 2 are H. In formula (2), R represents H or a carboxy group, and A1 and A2 represent H, OH, or a group represented by formula (3). In formula (3), one of X, Y, and X represents the bonding site of the C in formula (2), and the remainders represent H or –CH(OH)COOH.)