A running web is coated with a coating liquid containing polyvinyl alcohol by means of a slide hopper that has a slide surface of which the inclining angle with respect to a horizontal plane is within a range between 5null and 30null; a thickness T nullmmnull of the coating liquid on the running web is smaller than a thickness S nullmmnull of the coating liquid flowing down along the slide surface; a bead clearance CL nullmmnull between the end of the slide surface and the running web at the bead part is determined in accordance with the thickness T nullmmnull of the coating liquid on the running web in an inequality, Tnull0.05