To provide the emulsion of an acrylic copolymer suitable for an emulsion type adhesive excellent in anchoring property to a substrate even by making the adhesive layer directly in contact with water before application, and without reducing bonding performance against a flexible material to be bonded such as human skin even under a condition of being immersed in water.

This acrylic copolymer emulsion having 80,000 to 600,000 weight-average molecular weight is obtained by performing the emulsion polymerization of mixed liquid containing 100 pts.wt. of an acrylic monomer consisting of (a) 50 to 85 wt.% 4-12C alkyl acrylate, (b) 1 to 10 wt.% 1-4C alkyl methacrylate, (c) 10 to 30 wt.% 1-3C alkyl acrylate and (d) 2 to 10 wt.% mixture having (1/1) to (1/5)=(acrylic acid)/(methacrylic acid) ratio, and (e) 10 to 30 pts.wt. of a hydrogenated type rosin ester having 82 to 110C softening point and 2 to 20 mg KOH/g acid value in the presence of a chain transfer agent.