A method for producing a circular polarization separation sheet comprising: a coating layer forming step of applying on a substrate a photopolymerizable composition containing a photopolymerization initiator and a polymerizable cholesteric liquid crystal compound, to obtain a coating layer; and a resin layer forming step of converting said coating layer into a resin layer having a cholesteric regularity, wherein said resin layer forming step includes: a selected ultraviolet light irradiation step (i) of cooling the coating layer to 20 to 40°C, and then irradiating said coating layer with a selected ultraviolet light having an illumination intensity of 0.1 mW/cm 2 or more and less than 10 mW/cm 2 under a temperature at 20 to 40°C for 0.1 to 6 seconds in the presence of oxygen wherein a gradient in the polymerization degree occurs along the thickness direction of the coating layer, the selected ultraviolet light does not cause complete curing; a cholesteric regularity adjustment step (ii) of changing a cycle of the cholesteric regularity in said coating layer; and a coating layer curing step (iii) of curing said coating layer, to realize a complete curing of the coating layer, wherein said selected ultraviolet light irradiation step (i) and said cholesteric regularity adjustment step (ii) are repeated more than once in said resin layer forming step, and wherein, in said selected ultraviolet light irradiation step (i), irradiation is given not on a front surface of the coating layer but on a surface of the substrate and thereby on a back surface of the coating layer facing the substrate. a coating layer forming step of applying on a substrate a photopolymerizable composition containing a photopolymerization initiator and a polymerizable cholesteric liquid crystal compound, to obtain a coating layer; and a resin layer forming step of converting said coating layer into a resin layer having a cholesteric regularity, wherein said resin layer forming step includes: a selected ultraviolet light irradiation step (i) of cooling the coating layer to 20 to 40°C, and then irradiating said coating layer with a selected ultraviolet light having an illumination intensity of 0.1 mW/cm 2 or more and less than 10 mW/cm 2 under a temperature at 20 to 40°C for 0.1 to 6 seconds in the presence of oxygen wherein a gradient in the polymerization degree occurs along the thickness direction of the coating layer, the selected ultraviolet light does not cause complete curing; a cholesteric regularity adjustment step (ii) of changing a cycle of the cholesteric regularity in said coating layer; and a coating layer curing step (iii) of curing said coating layer, to realize a complete curing of the coating layer, a selected ultraviolet light irradiation step (i) of cooling the coating layer to 20 to 40°C, and then irradiating said coating layer with a selected ultraviolet light having an illumination intensity of 0.1 mW/cm 2 or more and less than 10 mW/cm 2 under a temperature at 20 to 40°C for 0.1 to 6 seconds in the presence of oxygen wherein a gradient in the polymerization degree occurs along the thickness direction of the coating layer, the selected ultraviolet light does not cause complete curing; a cholesteric regularity adjustment step (ii) of changing a cycle of the cholesteric regularity in said coating layer; and a coating layer curing step (iii) of curing said coating layer, to realize a complete curing of the coating layer, wherein said selected ultraviolet light irradiation step (i) and said cholesteric regularity adjustment step (ii) are repeated more than once in said resin layer forming step, and wherein, in said selected ultraviolet light irradiation step (i), irradiation is given not on a front surface of the coating layer but on a surface of the substrate and thereby on a back surface of the coating layer facing the substrate.