A special visual effect is achieved. An optical device includes a light-reflecting interface provided with a first relief structure including first recesses or protrusions arranged two-dimensionally, the first relief structure emitting a first diffracted light when illuminated with a light, and a light-transmitting interface disposed in front of the light-reflecting interface and having a reflectance smaller than that of the first interface, the light-transmitting interface being provided with a second relief structure including second recesses or protrusions arranged two-dimensionally, and the second relief structure emitting a second diffracted light when illuminated with the light.