A substrate surface processing apparatus is provided. In the substrate surface processing apparatus, a spin chuck holds a substrate thereon by suction, spins the substrate, and moves up and down the substrate. An upper bowl and a lower bowl surround the spin chuck for receiving a processing solution by which the surface of the substrate is processed. An air outlet is positioned under the lower bowl for exhausting air from the upper and lower bowls. A flow separation protrusion is formed within the upper bowl. It separates an air flow around the substrate into an upward air flow and a downward air flow and exhausts the downward air flow through the air outlet.