To provide a small pump device with a screw pump having a lead screw whose pumping capability is sufficient.

The small pump device 1 comprises an introduction part 10 for introducing liquid, a discharge part 11 for discharging the liquid introduced by the introduction part 10 from a position on the upper side of the introduction part 10, and a liquid passage 12 connecting the introduction part 10 to the discharge part 11. In the liquid passage 12, a pumping mechanism is provided which consists of the screw pump 13 having the lead screw 16. The lead screw 16 is formed as one-line wound one having an advance angle of 5-15°.