Estimating the spectral distribution of an object requires not only the time of image sensing by a multi-spectrum camera but also, in order to process all band information acquired, large amounts of memories for storing all the band information of all pixels, and the processing time for processing all the band information. In this invention, when the spectral distribution data of a total wavelength region is to be estimated from color data and a plurality of spectral distribution data different in wavelength region, the color data is acquired, and, on the basis of the configuration of spectral distribution data defined in accordance with the acquired color data, spectral distribution data necessary for the estimation is acquired. In this way, the spectral distribution data of the total wavelength region is estimated.