Viscosity regulator for water-based resin and water-based coating composition

Provided are: a viscosity regulator for an aqueous resin, the viscosity regulator being capable of reducing the amount of a neutralizing base used in the viscosity regulator, having excellent viscosity-imparting effect, pseudoplasticity-imparting effect, and thermal stability, and being capable of exhibiting these effects at a wide range of pH from acidic to alkaline; the invention relates to a viscosity regulator for water-based resin. A viscosity-imparting composition containing: a viscosity-imparting component (X) containing 1-30 mass% of a diamide compound (A) obtained by reacting a diamine component (A1) selected from the group consisting of C2-12 diamines and/or a hydrogenated castor oil (A ') with a monocarboxylic acid component (A2) selected from the group consisting of C2-12 diamines; the monocarboxylic acid component (A2) is selected from the group consisting of monocarboxylic acids having at least a hydroxyl group; and 5-99 mass% of a first solvent (C) having at least one substituent selected from