The rolling bearing of the invention to be incorporated in the compressor for fuel cell system comprises a fluorine-based grease containing a fluororesin and a fluorine-based oil, a urea grease containing a urea compound and a synthetic oil or a lithium complex grease containing a lithium complex and a synthetic oil encapsulated therein. In this arrangement, the grease deterioration of the rolling bearing incorporated in the compressor for force-feeding various fluids between machines can be prevented, making it possible to provide a fuel cell system which can maintain stable operation over an extended period of time.