A resin composition containing heat-expandable microspheres including a thermoplastic resin shell and a thermally vaporizable blowing agent encapsulated therein and at least one base resin selected from rubbers, olefin resins and thermoplastic elastomers. The thermoplastic resin is a polymer of a polymerizable component containing N-substituted maleimide and a nitrile monomer containing methacrylonitrile. Also disclosed are molded articles manufactured by molding the resin composition.