Emitting illumination light (L1) and auxiliary light (L2) onto an observation target (10) simultaneously and outputting an obtained RGB image signal to an estimated spectroscopic data calculation unit (180) and an image processing unit (181). The estimated spectroscopic data calculation unit (180) calculates, with respect to each pixel, an estimated spectroscopic data value of the auxiliary light (L2) and an estimated spectroscopic data value of reference light using the RBG image signal and estimated matrix data. A special superimposed image generation unit (187) calculates a light intensity ration r from estimated spectroscopic data values of auxiliary light (L2) and reference light, generates signal m based on the light intensity ratio r, and generates a quasi reflectivity information based special image using the signal m and a correspondence table T stored in a memory (190).
