MICROPOROUS FILM AND MANUFACTURING METHOD THEREFOR

The present invention relates to a porous membrane including cellulose fibers, wherein the cellulose fibers are obtained from a mixture of: more than 50% by weight of (1) first raw material cellulose fibers having a surface area determined by congo red coloring of 250 m/g or more and 500 m/g or less; and less than 50% by weight of (2) second raw material cellulose fibers having a surface area determined by congo red coloring of 150 m/g or more and less than 250 m/g. The porous membrane according to the present invention can provide a separator for electrochemical devices with superior properties, at a reasonable cost.