An optical device is provided and includes a substrate having a three-dimensionally random concave-convex shape on the surface thereof, and a hard coat layer formed on the substrate, wherein a projection height with the maximum frequency on the substrate surface falls within the range of 1.5 μm or more and not more than 10 μm. Projections larger than the projection height with the maximum frequency on the substrate surface have a height falling within +3 μm from a central value of the projection height with the maximum frequency. A length RSm in a lateral direction of concaves and convexes on the substrate surface is 55 μm or more and not more than 500 μm.