To provide a polymerization-stable and water-resistant emulsion in which an olefinic polymer and a vinyl polymer are conjugated.

The process for producing the emulsion comprises adding an emulsion (E) of a mixture (M) of an emulsifier and a vinyl monomer to an emulsion of a graft copolymer in which an olefinic polymer is graft-polymerized with a hydrophilic polymer and emulsion-polymerizing the mixture at a polymerization temperature of not higher than 65°C. A coating composition having a good contact with olefinic polymers is produced from the emulsion.