In order to provide a general-purpose aqueous primer composition requiring no organic solvent and capable of improving adhesive strength and durability while ensuring an adequate application life required for the work of primer coating process, a primer composition according to the present invention contains (a) a modified polyisocyanate obtained by reaction of polyisocyanate; an emulsifying agent having an active hydrogen group reactable to an isocyanate group; and a silane coupling agent having an active hydrogen group reactable to an isocyanate group and (b) a core shell emulsion having a core layer of a rubbery polymer and a shell layer of a glassy polymer and having an active hydrogen group reactable to an isocyanate group in the core layer and/or the shell layer.
