Provided is a method of producing a resin porous body using a water-insoluble polymer, the method being excellent in terms of simplicity and capable of suppressing formation of a skin layer. A method of producing a resin porous body disclosed herein includes the steps of: preparing a coating liquid in which a water-insoluble polymer is dissolved and insulating particles are dispersed in a mixed solvent containing a good solvent for the water-insoluble polymer and a poor solvent for the water-insoluble polymer; coating the coating liquid on a substrate; and removing the mixed solvent from the coated coating liquid by vaporization. The poor solvent has a boiling point higher than a boiling point of the good solvent. Pores are formed by removing the mixed solvent by vaporization to obtain a porous body.