A fluidity modifier for a coating material or the like contains an ester resin represented by the following general formula (I) or general formula (II) (Y represents a hydrogen atom or a monocarboxylic acid residue having 1 to 9 carbon atoms, G represents an aliphatic diol residue having 2 to 9 carbon atoms, A represents an aliphatic dicarboxylic acid residue having 2 to 10 carbon atoms, X represents a dicarboxylic acid residue having 1 to 8 carbon atoms, Z represents a monoalcohol residue having 2 to 10 carbon atoms, n represents the number of repeating units and is an integer of 0 to 30, and m represents the number of repeating units and is an integer of 0 to 30; G and A may be the same or different for each repeating unit, and a plurality of G may be the same as or different from each other).