According to one embodiment, a supercritical drying method for a semiconductor substrate comprises introducing a semiconductor substrate, a surface of the semiconductor substrate being wet with a water-soluble organic solvent, to the inside of a chamber, hermetically sealing the chamber and increasing a temperature inside the chamber to not lower than a critical temperature of the water-soluble organic solvent, thereby bringing the water-soluble organic solvent into a supercritical state, decreasing a pressure inside the chamber and changing the water-soluble organic solvent in the supercritical state to a gas, thereby discharging the water-soluble organic solvent from the chamber, starting a supply of an inert gas into the chamber as the pressure inside the chamber decreases to atmospheric pressure, and cooling the semiconductor substrate in a state where the inert gas exists inside the chamber.