The purpose of the present invention is to provide a film with little impurities that uses cellulose as a starting material and is thin, uniform, and compact and to provide an electrolytic capacitor that can be made small and/or given high capacity by using this film as a separator. A cellulose solution in which cellulose is dissolved in an amine oxide-based solvent is formed into a film form, and the cellulose solidified and regenerated by immersion in water or a poor solvent for the amine oxide-based solvent. After the regenerated cellulose has been washed in water and the amine oxide-based solvent eliminated, a cellulose film that is thin, uniform, and compact with little impurities is obtained by drying. A capacitor element is fabricated by disposing the cellulose film that is obtained between an anode aluminum foil and cathode aluminum foil as a separator and winding. This capacitor element is impregnated with an electrolyte by immersion in a liquid electrolyte and then put into a case followed by sealing and aging. An electrolytic capacitor that is made small and/or given high-capacity is thus provided.