A draw solute for forward osmosis may include a copolymer including a first structural unit, where a temperature-sensitive side chain is graft polymerized, and a second structural unit including a hydrophilic functional group. The temperature-sensitive side chain may include a structural unit for a side chain including a temperature-sensitive moiety. The temperature-sensitive moiety may be represented by Chemical Formula 1, Chemical Formula 2, or Chemical Formula 3: wherein R1 and R2 are each independently hydrogen or a linear or branched C3 to C5 alkyl group, provided that at least one of R1 and R2 is not hydrogen, R3 is a C3 to C5 alkylene group, and R4 is a linear or branched C3 to C5 alkyl group. The draw solute may be used to form an osmosis draw solution for use in a forward osmosis water treatment device and method.