Provided is a substrate processing apparatus. The substrate treating apparatus includes a processing chamber, a substrate supporting unit, a plasma generation unit, a gas supplying unit, an exhaust adjusting unit, or the like. Residual gas and reaction by-products are generated in a chamber after a substrate is treated by using a gas supplied from the gas supplying unit or plasma excited by the plasma generation unit. The gas exhaust adjusting unit adjusts discharge amounts of residual gas and reaction by-products to adjust residence time or pressure of gas, plasma, or the like in the apparatus, thereby controlling a uniformity of the substrate treating process.