Disclosed are a substrate processing apparatus that allow a chemical liquid to penetrate deeply into a gap between patterns of a substrate. The substrate processing apparatus includes a housing having a processing space defined therein in which a substrate is processed; a substrate support installed in the processing space so as to be rotatable about a rotation axis and configured to support the substrate; a chemical liquid supply disposed on top of the substrate support and configured to spray a chemical liquid toward an upper surface of the substrate supported on the substrate support; and a controller configured to repeatedly apply a first rotation control signal and a second rotation control signal indicating different rotation speeds to the substrate support so as to generate an inertial behavior of the chemical liquid coated on the substrate.