An imaging device includes a filter, an imaging element, a lens, a spectral image generator, and an exposure adjuster. The filter includes a plurality of filter areas having different spectral transmission characteristics. The imaging element receives light transmitted through the filter and outputs image information. The lens array includes a plurality of lenses arranged approximately parallel to a light receiving surface of the imaging element and is arranged between the filter and the imaging element. The spectral image generator generates a plurality of spectral images respectively corresponding to the plurality of filter areas on the basis of the image information output by the imaging element. The exposure adjuster adjusts an exposure time of the imaging element on the basis of luminance values of the spectral images.