Disclosed is a substrate processing apparatus capable of drying a substrate to be processed while suppressing a pattern collapse or occurrence of contamination. In a processing vessel, a substrate is immersed in a liquid in the longitudinal direction, and the liquid is pushed out by a substitution fluid of a supercritical state to be discharged from the processing vessel. Thereafter, the substitution fluid subjected to the substitution with the liquid is discharged from the processing vessel to depressurize the processing vessel, and the substitution fluid is changed from the supercritical state to a gaseous state to dry the substrate.