A liquid can be delivered with a simple configuration. A liquid delivery method includes allowing a liquid to flow in a tube having elasticity depending on a pressure of a gas filled in an inner space between a tube housing covering an outside of the tube and an outer surface of the tube; obtaining a magnitude of a pressure of the liquid flowing in the tube as a first value; obtaining a magnitude of the pressure of the gas filled in the inner space as a second value; calculating a difference between the first value and the second value as a third value; and detecting a status of the tube on the basis of the third value.