To provide a liquid feeding system in which all the flow passages in contact with liquid can be filled with a sterilizing gas, and which can reliably discharge the sterilizing gas to the outside of the liquid feeding system.

A liquid feeding system 100 includes a medical solution bag 101, a constant flow rate valve 103, a pump 104, and an air vent filter 160. The pump 104 includes a suction hole 141, a discharge hole 142, and check valves 143, 144. The constant flow rate valve 103 includes: a valve housing 110; and a diaphragm 120 constituting a first valve chest 111 and a second valve chest 112 by dividing the inside of the valve housing 110. A first opening 115, a second opening 117, and a third opening 118 are formed in the valve housing 110. The air vent filter 160 includes an inflow hole 161, an outflow hole 162, and a ventilation hole 163. The air vent filter 160 prevents a medical solution from passing to an outside through the ventilation hole 163, and allows only gas to pass through the ventilation hole 163.