An optical element (10, 50) comprising: a first layer; a second layer in contact with the first layer; and a third layer in contact with the second layer, each layer having light transmitting properties, wherein the first layer is a resin layer having a first refractive index n1, and has a first surface in contact with the second layer, and includes a grating structure composed of concave and convex portions in at least part of the first surface, the second layer is a dielectric layer having a second refractive index n2 higher than the first refractive index n1, and has a concavo-convex shape that follows the grating structure, the third layer is a resin layer having a third refractive index n3 lower than the second refractive index n2, the first surface has a concavo-convex surface, the grating structure includes a first grating structure (11G1) and a second grating structure (11G2), the concavo-convex surface includes a first region (11S1) in which the first grating structure (11G1) is located, and a second region (11S2) in which the second grating structure (11G2) is located and which is located close to the first region (11S1) in plan view, as viewed perpendicular to the first surface, an azimuth angle of the first grating structure (11G1) and an azimuth angle of the second grating structure (11G2) are equal to each other, the first grating structure (11G1) and the second grating structure (11G2) have a grating period d in a range of 250 nm or more and 500 nm or less, and a difference between the grating period d1 of the first grating structure (11G1) and the grating period d2 of the second grating structure (11G2) is 20 nm or more, wherein the difference between the first refractive index n1 and the third refractive index n3 is 0.2 or less, and wherein the optical element (10, 50) further comprises a resin layer located on a side of the first layer opposite to that facing the second layer, wherein the first layer has a hardness higher than a hardness of the resin layer and higher than a hardness of the third layer, the first layer is made of an ultraviolet curable resin, the first layer has a thickness in a range of 1 μm or more and 10 μm or less, and the resin layer and the third layer are made of a thermoplastic resin. a first layer; a second layer in contact with the first layer; and a third layer in contact with the second layer, each layer having light transmitting properties, wherein the first layer is a resin layer having a first refractive index n1, and has a first surface in contact with the second layer, and includes a grating structure composed of concave and convex portions in at least part of the first surface, the second layer is a dielectric layer having a second refractive index n2 higher than the first refractive index n1, and has a concavo-convex shape that follows the grating structure, the third layer is a resin layer having a third refractive index n3 lower than the second refractive index n2, the first surface has a concavo-convex surface, the grating structure includes a first grating structure (11G1) and a second grating structure (11G2), the concavo-convex surface includes a first region (11S1) in which the first grating structure (11G1) is located, and a second region (11S2) in which the second grating structure (11G2) is located and which is located close to the first region (11S1) in plan view, as viewed perpendicular to the first surface, an azimuth angle of the first grating structure (11G1) and an azimuth angle of the second grating structure (11G2) are equal to each other, the first grating structure (11G1) and the second grating structure (11G2) have a grating period d in a range of 250 nm or more and 500 nm or less, and a difference between the grating period d1 of the first grating structure (11G1) and the grating period d2 of the second grating structure (11G2) is 20 nm or more, wherein the difference between the first refractive index n1 and the third refractive index n3 is 0.2 or less, and wherein the optical element (10, 50) further comprises a resin layer located on a side of the first layer opposite to that facing the second layer, wherein the first layer has a hardness higher than a hardness of the resin layer and higher than a hardness of the third layer, the first layer is made of an ultraviolet curable resin, the first layer has a thickness in a range of 1 μm or more and 10 μm or less, and the resin layer and the third layer are made of a thermoplastic resin.