An optical function device includes a base material layer, a semi-transparent layer formed on a principal plane of the base material layer, the semi-transparent layer reflecting light of incident light at a ratio determined in advance and passing remaining light; and a reflection prevention layer formed on a principal plane opposite to the principal plane of the base material layer with respect to the base material layer, the reflection prevention layer preventing reflection of the light passing through the base material layer. The image-capturing device includes an optical function device, a first light receiving device for receiving transmission light from the optical function device, and a second light receiving device for receiving reflection light from the optical function device.