disclosed is a coating die for coating a web with a solution , wherein the web is conveyed in a predetermined direction so as to run in the vicinity of the coating die ; comprising ; a body forming the coating die , a coating surface provided on the body at a position close to the running web ; a solution chamber provided in the body ; a feeding conduit provided in the body , wherein the solution is fed from the outside of the body to the solution chamber through the feeding conduit ; a slit provided in the body so as to connect the solution chamber and the coating surface , wherein the solution is fed from the solution chamber to the coating surface through the slit , and then the solution is transferred from the coating surface to the running web ; a dry surface provided on the body and positioned upstream of the coating surface in terms of the web - running direction ; and a polymer layer formed on at least one of the dry surface , an internal surface of the slit , and internal surfaces of the solution chamber and the feeding conduit , the polymer layer containing a polymer prepared by polymerizing a silane coupling agent having a fluorine containing alkyl group .