Provided are a wavelength conversion layer and a display device. A color conversion element comprises: a wavelength conversion layer; one or more low refractive layers which are disposed on and/or under the wavelength conversion layer and have a lower refractive index than the wavelength conversion layer; and one or more capping layers which are disposed between the wavelength conversion layer and the low refractive layers and/or on a surface opposite to a surface of each of the low refractive layers which faces the wavelength conversion layer.