There is provided a liquid supply method in which, when preparing a solution that can be used as washing water and the like by supplying a minute amount of chemicals and the like to ultrapure water, the amount of supply solution that is supplied can be accurately determined. In this liquid supply method, a solution is prepared by supplying a supply liquid to a primary fluid that is circulating in a primary fluid circulation tube (2). This liquid supply method uses a liquid supply apparatus (1) that includes: a supply section (3) that delivers the supply liquid; and a supply liquid circulation tube (4) that causes the supply liquid to flow from the supply section (3) to the primary fluid circulation tube (2), the internal diameter of the supply liquid circulation tube (4) being between 0.01 and 1 mm. When the supply solution is supplied from the supply section (3) to the primary fluid circulation tube (2) via the supply liquid circulation tube (4), a pressure P1 of the supply liquid in the supply section (3) and a pressure P2 of the primary fluid in the primary fluid circulation tube satisfy the formula P1−P2>0.