In a developing processing of a wafer having a resist film low in the dissolving rate in a developing solution formed thereon and subjected to an exposure treatment, a developing solution of a low concentration is supplied first onto a wafer and the wafer is left to stand for a prescribed time to permit a developing reaction to proceed, followed by further supplying a developing solution having a concentration higher than that of the developing solution supplied first onto the wafer, leaving the substrate to stand and subsequently rinsing the wafer, thereby improving the uniformity of the line width in the central portion and the peripheral portion of the wafer.