An observation device includes a light source unit capable of adjusting a quantity of 390-490 nm illuminating light according to a B1 range and a B2 range having a longer wavelength than the B1 range, and an imaging element that images reflected light from a subject irradiated with illuminating light. The light source unit changes the light quantity ratio of the B1 range to the B2 range depending on whether white light imaging is conducted or narrow band imaging is conducted. The imaging element includes RGB color filters arranged according to pixels and the R color filter transmits more light in an R range and the B1 range than light in the second B range and has a spectral characteristic that satisfies a predetermined conditional formulae.
