A stay of a liquid can be suppressed. A pump 100 includes a tube 102, having elasticity, in which a liquid as a target to be delivered flows; a tube housing 104 which covers an outside of the tube 102 and keeps a gas in an inner space V between an outer surface of the tube 102 and the tube housing 104; and an electropneumatic regulator RE configured to supply the gas into the inner space V and discharge the gas from the inner space V.