An optical device comprising: a relief structure formation layer having a main surface, the main surface including first and second regions (R1, R2) adjacent to each other, the first region including first and second sub-regions (SR1, SR2), the first sub-region being adjacent to the second region and extending along a boundary between the first and second regions (R1, R2), the second sub-region being adjacent to the second region with the first sub-region interposed therebetween, the second region being provided with recesses or protrusions and having a ratio of surface area to apparent area greater than that of the first region; a first layer made of a first material having a refractive index different from that of a material of the relief structure formation layer (1 10) and covering the second sub-region only, the first layer having a surface profile corresponding to a surface profile of the second sub-region; and a second layer made of a second material different from the first material and covering the first layer, a ratio of an amount of the second material at a position of the second region to the apparent area of the second region being zero or smaller than a ratio of an amount of the second material at the position of the second sub-region to the apparent area of the second sub-region, wherein the second layer faces the entire surface of the first region, and a first orthogonal projection of a contour of the first layer on the main surface has a shape similar to a second orthogonal projection of a contour of the second layer on the main surface and is surrounded by the second orthogonal projection, or a part of the first orthogonal projection overlaps a part of the second orthogonal projection and the remainder of the first orthogonal projection has a shape similar to the remainder of the second orthogonal projection and is surrounded by the second orthogonal projection, characterized in that the second layer is a vapour-deposited layer and in that the second material is inorganic material. a relief structure formation layer having a main surface, the main surface including first and second regions (R1, R2) adjacent to each other, the first region including first and second sub-regions (SR1, SR2), the first sub-region being adjacent to the second region and extending along a boundary between the first and second regions (R1, R2), the second sub-region being adjacent to the second region with the first sub-region interposed therebetween, the second region being provided with recesses or protrusions and having a ratio of surface area to apparent area greater than that of the first region; a first layer made of a first material having a refractive index different from that of a material of the relief structure formation layer (1 10) and covering the second sub-region only, the first layer having a surface profile corresponding to a surface profile of the second sub-region; and a second layer made of a second material different from the first material and covering the first layer, a ratio of an amount of the second material at a position of the second region to the apparent area of the second region being zero or smaller than a ratio of an amount of the second material at the position of the second sub-region to the apparent area of the second sub-region, wherein the second layer faces the entire surface of the first region, and a first orthogonal projection of a contour of the first layer on the main surface has a shape similar to a second orthogonal projection of a contour of the second layer on the main surface and is surrounded by the second orthogonal projection, or a part of the first orthogonal projection overlaps a part of the second orthogonal projection and the remainder of the first orthogonal projection has a shape similar to the remainder of the second orthogonal projection and is surrounded by the second orthogonal projection,