Abstract: A substrate treating apparatus for drying substrates in a solvent atmosphere after treating the substrates with a treating liquid. The apparatus includes a treating tank for storing the treating liquid, a holding mechanism for holding the substrates, the holding mechanism being movable at least between a treating position in the treating tank and a drying position above the treating tank, a chamber enclosing the treating tank, a solvent vapor supply device for supplying solvent vapor into the chamber, a concentration measuring device for measuring solvent concentration in the chamber, and an exhaust device for exhausting gas from the chamber. A controller causes the exhaust device to decompress an interior of the chamber, and causes the solvent vapor supply device to supply the solvent vapor into the chamber, after treating the substrates in the treating position in the treating tank with deionized water serving as the treating liquid.