In observation of organism tissue with white light or special light, desired tissue information of the organism tissue is obtained in a clearer state suitable to diagnosis. A first light source 51 using a semiconductor light emitting device as an emission source a second light source 53 using, as an emission source, a semiconductor light emitting device of a different emission wavelength from the first light source 51 a wavelength converting member 57 excited for light emission by light emitted from at least one of the first light source 51 and the second light source 53 and light quantity ratio changing means 55 changing a light quantity ratio between the light emitted from the first light source 51 and the light emitted from the second light source 53 are included, and therefore, the light emitted from the first light source 51 and the light emitted from the second light source 53 may be arbitrarily generated so as to provide illumination light suitable to diagnosis in accordance with an absorption characteristic and a scattering characteristic of organism tissue. Therefore, desired tissue information of the organism tissue may be obtained in a clearer state.
