The invention includes a lower guide unit which obliquely extends downward to an outside from a position closely opposed to a peripheral edge portion of a rear surface of the substrate held on the substrate holding unit, and is formed in an annular shape in a circumferential direction of the substrate; and an upper guide unit which has an upper end surface located at a substantially same height as a front surface of the substrate held on the substrate holding unit, forms a lower annular flow path between the upper guide unit and the lower guide unit for guiding downward together with a gas flow a treatment solution scattering from the substrate, is formed in an annular shape opposed to the lower guide unit to surround an outside lower region of the substrate, and has an inner peripheral surface having a longitudinal-sectional shape curved to bulge outward and extending downward.