Substrate processing apparatus and cleaning method of lock key

A cleaning method of cleaning a lock key in a substrate processing apparatus including a pressure vessel having therein a drying chamber in which a substrate is dried by replacing a liquid film formed on a top surface of the substrate with a supercritical fluid, a cover body configured to close an opening of the drying chamber, and the lock key that restricts a movement of the cover body, the lock key being configured to be moved up and down between a lock position where the lock key restricts the cover body from moving from a closing position where the cover body closes the opening toward an opening position where the cover body opens the opening, and a lock release position where the lock key allows the cover body to move between the closing position and the opening position, the cleaning method comprising:

• preparing a brush at a position where the brush comes into contact with the lock key when the lock key is moved between the lock position and the lock release position;
• and
• removing particles adhering to a surface of the lock key from the lock key by moving the lock key between the lock position and the lock release position to rub the lock key with the brush.