A method for manufacturing a membrane switch member that can be manufactured easily and that can be caused to function as an electrostatic sensor even when a protruding portion is pressed. Injection molding by injecting a material including a supercritical fluid gas and a resin material in a mixed state; and, after the injection molding, removing a first mold from a second mold, causing gas produced within the injection molded resin to grow in concave portions, thereby causing the concave portions to invert to a protruding state; and manufacturing a membrane switch member in which voids are formed between the protruding portions and a molding resin layer, and portions other than the portions corresponding to the protruding portions are adhered to the resin layer by an adhesion layer.