An optical element comprising: a first optical layer having a light emission surface; a wavelength-selective reflective layer provided on the first optical layer; and a second optical layer provided on the wavelength-selective reflective layer and having a light incidence surface, wherein the wavelength-selective reflective layer has a structure including at least five layers in which high refractive-index layers, having a high refractive-index in the visible region, and metal layers are alternately laminated to each other, when a geometric film thickness L of the entire wavelength-selective reflective layer is 100 nm, a ratio α of an optical film thickness of the entire metal layers to an optical film thickness of the entire high refractive-index layers and a ratio β of an optical film thickness of a third high refractive-index layer from one of a first optical layer side and a second optical layer side to an optical film thickness of a first high refractive-index layer therefrom are included in a first region surrounded by the following formulas α = − 0.0002 β 2 + 0.0055 ⁢ β + 0.0057 α = − 0.0002 β 2 + 0.0045 ⁢ β − 0.0067 α = − 4 × 10 − 5 β 2 + 0.001 ⁢ β + 0.0099 α = 0.009403, when the geometric film thickness L of the entire wavelength-selective reflective layer is 120 nm, the ratio α and the ratio β are included in a second region surrounded by the following formulas α = − 0.0003 β 2 + 0.0074 ⁢ β + 0.0033 α = − 0.0014 β 2 + 0.0191 ⁢ β − 0.0422 α = − 9 × 10 − 5 β 2 + 0.0015 ⁢ β + 0.0084 α = 0.007709, and when the geometric film thickness L of the entire wavelength-selective reflective layer is in a range of 100 to 120 nm, the ratio α and the ratio β are included in a space enclosed by the first region, the second region, and the following formulas β− 0.6 / 0.1 = α − 0.00771 / 0.0016942 = 120 − L / 20 β− 3.6 / 0.8 = α − 0.00771 / 0.0016942 = 120 − L / 20 β− 4.25 / 2.25 = α − 0.0133 / 0.00101652 = 120 − L / 20 β− 0.9 / 0.1 = α − 0.00974 / 0.00118594 = 120 − L / 20 wherein α and β are determined for light with a wavelength of 550 nm. a first optical layer having a light emission surface; a wavelength-selective reflective layer provided on the first optical layer; and a second optical layer provided on the wavelength-selective reflective layer and having a light incidence surface, wherein the wavelength-selective reflective layer has a structure including at least five layers in which high refractive-index layers, having a high refractive-index in the visible region, and metal layers are alternately laminated to each other, when a geometric film thickness L of the entire wavelength-selective reflective layer is 100 nm, a ratio α of an optical film thickness of the entire metal layers to an optical film thickness of the entire high refractive-index layers and a ratio β of an optical film thickness of a third high refractive-index layer from one of a first optical layer side and a second optical layer side to an optical film thickness of a first high refractive-index layer therefrom are included in a first region surrounded by the following formulas α = − 0.0002 β 2 + 0.0055 ⁢ β + 0.0057 α = − 0.0002 β 2 + 0.0045 ⁢ β − 0.0067 α = − 4 × 10 − 5 β 2 + 0.001 ⁢ β + 0.0099 α = 0.009403, when the geometric film thickness L of the entire wavelength-selective reflective layer is 120 nm, the ratio α and the ratio β are included in a second region surrounded by the following formulas α = − 0.0003 β 2 + 0.0074 ⁢ β + 0.0033 α = − 0.0014 β 2 + 0.0191 ⁢ β − 0.0422 α = − 9 × 10 − 5 β 2 + 0.0015 ⁢ β + 0.0084 α = 0.007709, and when the geometric film thickness L of the entire wavelength-selective reflective layer is in a range of 100 to 120 nm, the ratio α and the ratio β are included in a space enclosed by the first region, the second region, and the following formulas β− 0.6 / 0.1 = α − 0.00771 / 0.0016942 = 120 − L / 20 β− 3.6 / 0.8 = α − 0.00771 / 0.0016942 = 120 − L / 20 β− 4.25 / 2.25 = α − 0.0133 / 0.00101652 = 120 − L / 20 β− 0.9 / 0.1 = α − 0.00974 / 0.00118594 = 120 − L / 20