An imaging device includes: an imaging unit configured to output an imaging signal; an illumination unit configured to emit respective beams of light of a plurality of colors; a color separation unit configured to separate the imaging signal into a plurality of signals corresponding to the plurality of colors; an interest color setting unit configured to set a color corresponding to a wavelength band of interest as an interest color; a comparison unit configured to compute a ratio between a detection value of a signal corresponding to an interest color set by the interest color setting unit and a detection value of a signal of another color corresponding to a wavelength band different from the wavelength band corresponding to the interest color; and a changing unit configured to change a light emission ratio between light corresponding to the interest color and light of the other color.