The UV-curable aqueous coating composition is characterized by using a UV-curable aqueous emulsion obtained by urethane reaction with a mixture including a poly-carbonate polyol or polyester polyol; an isocyanate compound; a urethane-reactive carboxylic acid; a UV-curable acrylic oligomer having 2 to 9 functional acrylate groups; a UV-curable acrylic monomer; and a urethane-reactive acrylate without an organic solvent. The aqueous composition provides good environmental acceptability and satisfactory film properties comparable to those of the prior oily UV-curable coating composition and, therefore, it is useful for coating various plastics.