A variable geometry system turbocharger includes an annular heat shield plate which shields heat from a turbine wheel side. The heat shield plate is integrally provided at a central part of a side surface of a bearing housing opposed to a back surface of a turbine disk. A first seal ring is provided between an inner peripheral surface of a first nozzle ring and an outer peripheral surface of the heat shield plate. A second seal ring is provided between an inner peripheral surface of a second nozzle ring and an outer peripheral surface of a protrusion of a turbine housing.