In a developing method for performing developing treatment of a substrate by supplying a developing solution onto a resist film formed on a surface of the substrate, the present invention controls a zeta potential of the surface of the substrate at a predetermined potential in the same polarity as that of a zeta potential of insoluble substances floating in the developing solution, thereby preventing or reducing the adhesion of the insoluble substances to the resist film and the substrate. This remedies the occurrence of development defects. The adhesion of the insoluble substances to the resist film and the substrate can also be prevented or inhibited by supplying an acid liquid to a liquid on the substrate, or controlling a pH value of the liquid on the substrate to control an absolute value of the zeta potential of the insoluble substances.