The invention discloses a liquid-replenishing device, which comprises a liquid storage tank, a chemical liquid medicine supply pipeline, an ultrapure water supply pipeline, an ultrapure water quantitative supply pipeline and a circulating pipeline, wherein the chemical liquid medicine supply pipeline provides chemical liquid medicine for the liquid storage tank; the ultrapure water supply pipeline provides ultrapure water for the liquid storage tank; the ultrapure quantitative supply pipeline quantitatively replenishes ultrapure water for the liquid storage tank; and one end of the circulating pipeline is connected with a liquid outlet of the liquid storage tank, and the other end of the circulating pipeline is connected with an inlet of the liquid storage tank. The liquid-replenishing device can quantitatively replenish liquid at regular time along with repeated use of the chemical liquid medicine and change of the concentration of the liquid medicine, and the certain concentration of the liquid medicine can be maintained, so that a process effect is guaranteed, and the liquid-replenishing device is simple in operation.