To provide a pump unit for delivering liquid increasing accuracy of a delivery quantity of liquid without requiring to provide a shut-off valve at a downstream side of a pump chamber, and to accurately control timing for closing the unit.

The pump unit for delivering liquid pressurizes an electrolyte in the pump chamber 11 by a drive member 13 driven in such a manner that volume of the pump chamber 11 is changed, and delivers the electrolyte from the delivery passage 62 communicating with the pump chamber 11 prescribed quantity by prescribed quantity. In the pump unit, the drive member 13 shuts off communication between the pump chamber 11 and the delivery passage 62 when the pressurization of the electrolyte by the drive member 13 is completed.