A substrate container includes a container housing having an opening for storing a substrate therethrough and a cover sealingly covering the opening, a fan motor mounted in the container housing for producing a circulating path of air in contact with the substrate in the container housing, and a particle removing filter and a gaseous impurity trapping filter which are disposed in the a portion of the circulating path which extends toward the substrate. A dehumidifying unit for dehumidifying a space in the container housing comprises a solid polymer electrolyte film disposed in the circulating path and voltage applying means for applying a voltage to the solid polymer electrolyte film to decompose water in air flowing in the circulating path thereby to dehumidify a space in the container housing.