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 120 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 = − 0.0003 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, when the geometric film thickness L of the entire wavelength-selective reflective layer is 140 nm, the ratio α and the ratio β are included in a second region surrounded by the following formulas α = − 0.0014 β 2 + 0.0136 ⁢ β − 0.0027 β = 10,132 α 2 − 241.39 ⁢ α + 4.747 α = − 0.0001 β 2 + 0.002 ⁢ β + 0.0074 α = 0.006523, and when the geometric film thickness L of the entire wavelength-selective reflective layer is in a range of 120 to 140 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 0.75 − β / 0.15 = α − 0.00652 / 0.00118594 = 140 − L / 20 3.65 − β / 0.05 = α − 0.00652 / 0.00118594 = 140 − L / 20 β − 3.3 / 0.95 = α − 0.01245 / 0.0008471 = 140 − L / 20 3.47 − β / 2.57 = α − 0.00754 / 0.00220246 = 140 − 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 120 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 = − 0.0003 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, when the geometric film thickness L of the entire wavelength-selective reflective layer is 140 nm, the ratio α and the ratio β are included in a second region surrounded by the following formulas α = − 0.0014 β 2 + 0.0136 ⁢ β − 0.0027 β = 10,132 α 2 − 241.39 ⁢ α + 4.747 α = − 0.0001 β 2 + 0.002 ⁢ β + 0.0074 α = 0.006523, and when the geometric film thickness L of the entire wavelength-selective reflective layer is in a range of 120 to 140 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 0.75 − β / 0.15 = α − 0.00652 / 0.00118594 = 140 − L / 20 3.65 − β / 0.05 = α − 0.00652 / 0.00118594 = 140 − L / 20 β − 3.3 / 0.95 = α − 0.01245 / 0.0008471 = 140 − L / 20 3.47 − β / 2.57 = α − 0.00754 / 0.00220246 = 140 − L / 20, wherein α and β are determined for light with a wavelength of 550 nm.