A pump unit (100) includes a plurality of piezoelectric pumps (1), a flow path-defining member (50), and a heat-dissipating part (60). The plurality of piezoelectric pumps (1) each include a first flow path for sucking and discharging of fluid. The flow path-defining member (50) includes a second flow path for connection to the first flow paths in the plurality of piezoelectric pumps (1). Heat generated in the plurality of piezoelectric pumps (1) is dissipated through the heat-dissipating part (60). The heat-dissipating part (60) is disposed between the flow path-defining member (50) and each of the plurality of piezoelectric pumps (1). The heat-dissipating part (60) has through-holes through which the first flow paths are connected to the second flow path.