Provided is a method for producing a separator which method less causes a tear in the separator. The method is a method for producing a separator by slitting, in a direction in which a separator original sheet (12b) being porous is conveyed, the separator original sheet (12b) into a plurality of separators (12a), including the steps of: (a) conveying the separator original sheet (12b) in a state where the separator original sheet (12b) is in contact with a roller (77); and (b) slitting the separator original sheet (12b) at a portion where the separator original sheet (12b) is in contact with the roller (77).