The substrate treating device performs a predetermined treatment on a substrate by immersing the substrate into a treating liquid that contains a predetermined chemical liquid and pure water. Further, the substrate treating device includes a treating tank in which a treating liquid with which a predetermined treatment is performed on the substrate is stored, a supply unit that supplies a chemical liquid or pure water to the treating tank, a discharge unit that discharges the treating liquid stored in the treating tank, and a control unit that controls supply of the treating liquid or the pure water by the supply unit. The control unit causes the supply unit to supply the chemical liquid or the pure water during performing the predetermined treatment.