The aggregation that a kind of protein aggregation inhibitor can inhibit protein is provided, even if when protein heats, in addition, it can inhibit to reduce even when the protein of protein active is heated, which feature includes the monomer that the polymer of sulfobetaine contains sulfobetaine general formula I expressions by polymerizable monomer composition. Wherein R1 is hydrogen atom or methyl, and R2 is the alkylidene containing 1-4 carbon, R3 be alkyl have carbon atom number 1-4, R4 alkylidene carbon atom number 1-4 and X-NH- groups or one-o- group.
