A substrate processing apparatus having improved uniformity and speed of reaction is provided. A substrate processing apparatus includes a body portion comprising a discharge path, a gas supply unit connected to the body portion, a first partition extending from the body portion, a second partition extending from the body portion and arranged between the gas supply unit and the first partition, and a substrate support unit configured to have surface-sealing with the first partition, wherein a first region between the first partition and the second partition and a second region between the gas supply unit and the second partition are connected to the discharge path.