NOVELTY - The apparatus has a pressure reduction drainage liquid container (33) pressure-reduced in a state in which a communicating vessel (35) is closed by the time a process liquid is discharged. An upper cover (11) is moved to an occlusion position such that solvent vapor is supplied to an inner tank (1) from a solvent vapor supply unit while connecting the vessel and making the container to discharge the liquid such that discharge is completed from the tank. A control unit (65) pressure-reduces the tank by a pressure reduction unit and performs a drying process with respect to a substrate (W).    USE - Batch type apparatus for drying a substrate i.e. semiconductor wafer, processed by process liquid i.e. pure water, with solvent vapor e.g. isopropyl alcohol, and a fluorine-type solvent such as hydrofluoro ether, for LCD, plasma display, organic electroluminescence display, field emission display, optical display, magnetic disk, magneto optical disk, photomask, and a solar cell. Can also be used as a single-wafer type apparatus.    ADVANTAGE - The control unit pressure-reduces the tank by the pressure reduction unit and performs the drying process with respect to the substrate such that a particle by the process liquid overflowing from the inner tank does not generate, and the substrate can be dried with high purity degree, so that solvent atmosphere can be formed in a short time. The container can be made to discharge the process liquid of the inner tank according to the pressure difference for a short time such that the drying process of a substrate can be performed in a short time, so that the through-put of the apparatus can be improved. The solvent vapor in the steam generation container is transduced into the inner tank by a pressure difference, so that carrier gas is not required while a solvent vapor density in the inner tank can be made high, so that amount of solvents condensed to the substrate can be increased, and dry efficiency can be improved.    DETAILED DESCRIPTION - The solvent vapor supply unit is a steam valve (23). The pressure reduction unit is a pressure reduction pump (41). An INDEPENDENT CLAIM is also included for a substrate processing method.    DESCRIPTION OF DRAWING(S) - The drawing shows a longitudinal cross-sectional view of a structure of a substrate processing apparatus. '(Drawing includes non-English language text)'    Substrate (W)    Inner tank (1)    Upper cover (11)    Steam valve (23)    Pressure reduction drainage liquid container (33)    Communicating vessel (35)    Pressure reduction pump (41)    Control unit (65)