To provide a water-based coating composition, capable of forming a coating film which is excellent in contamination resistance of retort treatment water and satisfies conveyance property and scratch resistance after retort treatment.

A water-based coating composition contains a copolymer (B) obtained by copolymerizing monomers (a)-(e) at the following polymerization ratio in the presence of a wax (A) having a melting point of 80°C or lower. (a) An N-alkoxymethyl (meth)acrylamide: 10-50 wt.%; (b) a monomer having ethylenic double bond and 8C or more alkyl: 1-10 wt.%; (c) a monomer having ethylenic double bond and hydroxyl: 1-10 wt.%; (d) a monomer having ethylenic double bond and carboxyl: 0.8-5 wt.%; and (e) a monomer having ethylenic double bond other than the monomers (a)-(d), which can form a polymer having a glass transition temperature of 45-105°C: 30-80 wt.%.