A light source and an illumination device are provided for making it possible to adjust influence of light over a living body while keeping good brightness and color taste of illumination light. A conversion characteristic in the degree of effect indicative of a relationship in a light wavelength between a living body reaction characteristic and an isochromatic characteristic of the visual perception is derived out and the light emitting intensity of a plurality of light emitters with different wavelength characteristics is controlled in accordance with the conversion characteristic, so as to adjust influence of light over a living body while keeping brightness and color taste of illumination light.