The inventive concept provides an apparatus for processing a substrate. The apparatus includes a mount; a processing liquid supply nozzle configured to provide a processing liquid to the substrate and a discharge container including: a base plate including a liquid outlet and an exhaust port; an inner wall standing on an inner circumference of the base plate; an outer wall standing on an outer circumference of the base plate; and a barrier standing on the base plate to separate a first space connected to the liquid outlet from a second space connected to the exhaust port. The apparatus further includes an inner cover configured to guide the flow of a processing liquid from the substrate supported by the mount to the first space of the discharge container; and a flow guide mounted in the first space of the discharge container.