To provide a preparation process of a composite resin emulsion of a polyurethane and an ethylenically unsaturated monomer polymer which has an excellent dispersion stability and yields a coated film, etc., showing an excellent transparency, solvent resistance, flexibility, mechanical properties, wear resistance, weather resistance, flexing resistance, hydrolysis resistance, etc.

In the presence of 100 pts.wt. polyurethane in a polyurethane emulsion which satisfies the following conditions (1)-(4), from 10 to 90 pts.wt. ethylenically unsaturated monomer is emulsion polymerized to prepare a composite resin emulsion. (1) The emulsion is prepared by allowing an isocyanate- terminated urethane prepolymer to react with a chain extender in an aqueous solution in the presence of a surfactant, (2) the polyurethane has from 1 to 20 mmol ethylenically unsaturated group per 100 g polyurethane, (3) the polyurethane has from 3 to 30 mmol neutralized carboxyl group and/or sulfonate group per 100 g polyurethane, (4) the emulsion contains from 0.5 to 10 g surfactant per 100 g polyurethane.