Provided is a release liner which includes a substrate derived from a poly(lactic acid), a biomass-derived plastic; and a releasable cured layer derived from a release agent. The releasable cured layer, even when employing an ultraviolet-curable silicone release agent as the release agent, is satisfactorily curable and exhibits good adhesion to the substrate. The release liner according to the present invention includes a poly(lactic acid) substrate; a release-treated layer present over at least one side of the substrate; and an undercoat layer lying between them. The undercoat layer is present in a mass of coating of typically from 0.1 to 5 g/m2 in solids content. The poly(lactic acid) substrate may contain a modifier. The release agent forming the release-treated layer may be an ultraviolet-curable silicone release agent. The ultraviolet-curable silicone release agent is preferably a cationically polymerizable ultraviolet-curable silicone release agent.