A pump unit can achieve significant size reduction while maintaining the performance thereof. Micropumps are arranged in a lattice pattern with rows and columns, and a discharge port of at least a micropump arranged in the most downstream row is directly connected to an integrated discharge port. The pump unit further includes: a discharge direct-connection mechanism for connecting respective discharge ports of a plurality of micropumps in a middle row directly to the integrated discharge port; an intake direct-connection mechanism for connecting respective intake ports of the micropumps directly to a fluid to be supplied first; a series-connection mechanism for connecting a discharge port of a micropump in an upstream row directly to an intake port of a micropump in a downstream row; and a controller for controlling the discharge direct-connection mechanism, the intake direct-connection mechanism, and the series-connection mechanism.