According to one embodiment, a supercritical drying method comprises cleaning a semiconductor substrate with a chemical solution, rinsing the semiconductor substrate with pure water after the cleaning, changing a liquid covering a surface of the semiconductor substrate from the pure water to alcohol by supplying the alcohol to the surface after the rinsing, guiding the semiconductor substrate having the surface wetted with the alcohol into a chamber, discharging oxygen from the chamber by supplying an inert gas into the chamber, putting the alcohol into a supercritical state by increasing temperature in the chamber to a critical temperature of the alcohol or higher after the discharge of the oxygen, and discharging the alcohol from the chamber by lowering pressure in the chamber and changing the alcohol from the supercritical state to a gaseous state. The chamber contains SUS. An inner wall face of the chamber is subjected to electrolytic polishing.