A developing treatment method supplies a developing solution onto a substrate to develop a resist film on the substrate with a predetermined pattern exposed thereon. The method supplies pure water to a central portion of the substrate to form a puddle of the pure water, and then moves a nozzle in a radial direction passing through a center of the substrate while supplying a developing solution to the puddle of the pure water from the nozzle with a wetted surface of the nozzle in contact with the puddle of the pure water, to form a puddle of a diluted developing solution on the substrate. The method then rotates the substrate to diffuse the puddle of the diluted developing solution over an entire surface of the substrate; and then supplies a developing solution to the substrate to develop the substrate.