Efficiently produced is a release liner including a plant-derived film as a substrate and having a good appearance, releasability, and adhesion. A method according to the present invention produces a release liner having a plant-derived film substrate and, on at least one side thereof, a release coat layer derived from a thermosetting silicone resin. The method includes the steps as follows: Step A of applying a thermosetting silicone release agent to at least one side of a plant-derived film substrate, the release agent containing 100 parts by weight of a thermosetting silicone resin and 0.05 to 0.55 part by weight of a curing catalyst; Step B of drying at 40° C. to 90° C. for 10 to 60 seconds after Step A; Step C of applying an ultraviolet ray at 50 to 300 mJ/cm2 after Step B; and Step D of aging at 30° C. to 70° C. for 12 to 240 hours after Step C.