An object of the present invention is to provide a thermoplastic resin composition exhibiting good impact resistance with maintaining excellent transparency, weather resistance and thermal stability and comprising a thermoplastic resin and at least one of a composite rubber and graft copolymer, the composite rubber comprises an isobutylene polymer and vinyl polymer which are preferably entangled with each other so as not to be separated from each other, and the graft copolymer is prepared by graft-polymerizing a vinyl monomer with the composite rubber, or comprising a thermoplastic resin and at least one of a composite rubber and graft copolymer, the composite rubber comprises an isobutylene polymer and vinyl polymer which are preferably entangled with each other so as not to be separated from each other, the isobutylene polymer has a reactive functional group on its molecular end and/or in its molecular chain and, if necessary, a moiety derived from a crosslinking agent and/or graft-linking agent, the vinyl polymer has a recurring unit derived from an acrylic acid ester and/or aromatic alkenyl compound and, if necessary, a moiety derived from the crosslinking agent and/or graft-linking agent, and the graft copolymer is prepared by graft-polymerizing a vinyl monomer with the composite rubber.