When coils of a vacuum pump unit are excited by energization, a piston equipped with magnets reciprocates in a cylinder. Thus, air is sucked in from an outlet passage of a diffuser of an ejector, and air discharged from the vacuum pump unit is supplied to an inlet of a nozzle of the ejector. Consequently, a fast jet occurs in a throat portion of the nozzle, and a negative pressure of higher degree of vacuum than that of the suction negative pressure of the vacuum pump unit is produced at a vacuum port of the ejector. The negative pressure is supplied from a negative pressure supply port. The ejector can supply a negative pressure of high degree of vacuum while reducing the load on the vacuum pump unit.