The present invention provides a method for removing wrinkles formed on a web, which is continuously transported through a plurality of guide members. The plurality of guide member includes a crown roller which has the diameter gradually increased toward the center thereof. The crown roller is placed in a transport path of the web and downstream of a first zone in which wrinkles are desirably removed, and the web is deformed in a second zone located downstream of the crown roller so as to at least decrease the width of the web, whereby the wrinkles in the first zone are removed. Even when the web is thin (10 m or less), without using particular backup means, wrinkles formed during transport and coating of the web can be removed. In addition, since wrinkles are appropriately removed, a coating film having a uniform thickness can be obtained by an extrusion coating method.