A substrate processing apparatus includes a chamber including a processing room for processing of a substrate using an introduced gas and an exhaust room for exhausting the gas in the processing room, a shield member provided near a side wall of the chamber to separate the processing room and the exhaust room and including a hole allowing the processing room and the exhaust room to communicate with each other, the shield member being driven in a vertical direction, and a hollow relay member connected to a pipe connected to an instrument outside the chamber and configured to be driven in a horizontal direction. When the shield member reaches an upper position, the relay member is driven inwardly of the chamber to be connected to the shield member at its inward end to allow the processing room and the pipe to communicate with each other through the hole.