SUBSTRATE PROCESSING APPARATUS AND METHOD FOR MAINTENANCE OF SUBSTRATE PROCESSING APPARATUS

The invention provides a substrate processing apparatus and a maintenance method of the substrate processing apparatus, which can smoothly maintain a drying unit. A substrate processing apparatus is provided with: a drying unit that dries a horizontal substrate by replacing a liquid film formed on the upper surface of the substrate with a supercritical fluid; and a control device. The drying unit is provided with a wall plate, an electromagnetic lock, a pressure sensor and a concentration sensor, the wall plate separates an internal space from an external space, and the electromagnetic lock is switched between a locked state and an unlocked state; the locking state is a state in which the wall plate is fixed at a position at which access from the external space to the internal space is restricted, and the unlocking state is a state in which the wall plate is allowed to move. Unlocking conditions for switching the state of the electromagnetic lock from the locking state to the unlocking state by the control de