To provide a coating method capable of forming a resin layer having good appearance without any stripes, and also preventing the release of air bubbles from the inside of a die coater so as not to cause the quality degradation of the resin layer.

In the method for coating the resinous coating liquid, a slot die coater which ejects the resinous coating liquid from a manifold onto a base material film via a slot is used to form the resin layer which becomes one component of an optical functional film. The slot of the slot die coater has a slot upstream region which is formed at the same height D1 as that of a communication port with the manifold and a slot downstream region which is formed at the same height D2 as that of a slot exit. D1 and D2 satisfy a following relational expression (1): 1D2/D15 and further D2 and thickness T of a coating film which is coated on the base material film and is in an undried state satisfy a following relational expression (2): D2/T20.