PURPOSE: To obtain a water-based coating material composition, containing anionic gel fine particles prepared by emulsifying a resin composition containing a specific maleinized oil, etc., and water-insoluble thermosetting crosslinking agent in a specific proportion in an aqueous medium and heating the resultant emulsion at a specific temperature and having excellent matte effects.

CONSTITUTION: A resin composition containing (A) a maleinized polybutadiene resin having negative charge in water in an amount of 100pts.wt. based on solid and (B) a water-insoluble thermosetting crosslinking agent capable of self-crosslinking and/or crosslinking with the component (A) by condensation or addition reaction, preferably melamine resin in an amount of 10W250pts.wt. based on solid is emulsified in an aqueous medium, preferably water and the resultant emulsion is heated at a temperature above the crosslinking temperature of the component (B), preferably under ordinary pressure. The resultant anionic fine gel particles are then contained to afford the aimed water-based coating material composition.