A pump unit comprising: a plurality of pump bodies (11, 12BD), each pump body (11, 12BD) of the plurality of pump bodies (11, 12BD) comprises a housing (16, 67), an inlet (11A, 12BA) formed in a surface of the housing (16, 67), an outlet (11B, 12BB) formed in the housing (16, 67), and a pump device (32, 61-63, 81-84, 91, 92) housed in the housing (16, 67); wherein each pump body (11, 12BD) of the plurality of pump bodies (11, 12BD) is configured to introduce a fluid outside its housing (16, 67) into its housing (16, 67) through its inlet (11A, 12BA) and is configured to discharge the introduced fluid to the outside of its housing (16, 67) through its outlet (11B, 12BB) by means of its pump device (32, 61-63, 81-84, 91, 92); and wherein the plurality of pump bodies (11, 12BD) comprises a pump body on an upstream side with respect to the fluid being introduced and discharged by the plurality of pump bodies (11, 12BD), and a pump body on a downstream side with respect to the fluid being introduced and discharged by the plurality of pump bodies (11, 12BD); and characterized by a jet nozzle provided at the outlet of the pump body on the upstream side, the jet nozzle including a jet port in a tip portion thereof being disposed at a position where a gap is formed between a peripheral portion of the inlet of the pump body on the downstream side and the tip portion such that a fluid jetted from the jet port is directly sucked into the inlet of the pump body on the downstream side and such that a fluid outside the pump bodies (11, 12BD) and in the vicinity of the gap can flow through the gap into the inlet of the pump body on the downstream side by being pulled by the fluid jetted from the jet port; wherein an opening size of the jet port is smaller than that of the inflow port and an opening shape of the jet port is confined within an opening shape of the inflow port; and the plurality of pump bodies (11, 12BD) are micro pumps. a plurality of pump bodies (11, 12BD), each pump body (11, 12BD) of the plurality of pump bodies (11, 12BD) comprises a housing (16, 67), an inlet (11A, 12BA) formed in a surface of the housing (16, 67), an outlet (11B, 12BB) formed in the housing (16, 67), and a pump device (32, 61-63, 81-84, 91, 92) housed in the housing (16, 67); wherein each pump body (11, 12BD) of the plurality of pump bodies (11, 12BD) is configured to introduce a fluid outside its housing (16, 67) into its housing (16, 67) through its inlet (11A, 12BA) and is configured to discharge the introduced fluid to the outside of its housing (16, 67) through its outlet (11B, 12BB) by means of its pump device (32, 61-63, 81-84, 91, 92); and wherein the plurality of pump bodies (11, 12BD) comprises a pump body on an upstream side with respect to the fluid being introduced and discharged by the plurality of pump bodies (11, 12BD), and a pump body on a downstream side with respect to the fluid being introduced and discharged by the plurality of pump bodies (11, 12BD); and characterized by a jet nozzle provided at the outlet of the pump body on the upstream side, the jet nozzle including a jet port in a tip portion thereof being disposed at a position where a gap is formed between a peripheral portion of the inlet of the pump body on the downstream side and the tip portion such that a fluid jetted from the jet port is directly sucked into the inlet of the pump body on the downstream side and such that a fluid outside the pump bodies (11, 12BD) and in the vicinity of the gap can flow through the gap into the inlet of the pump body on the downstream side by being pulled by the fluid jetted from the jet port; wherein an opening size of the jet port is smaller than that of the inflow port and an opening shape of the jet port is confined within an opening shape of the inflow port; and the plurality of pump bodies (11, 12BD) are micro pumps.