An identification-data memory is connected to a light-source identifying circuit. Data representing a type of characteristic quantity to be used in making an identification and identification points are stored in the identification-data memory with regard to each type of a plurality of light sources. Based upon input image data, a characteristic quantity is read out and identification points decided in accordance with the identification-data memory. The type of light source that was used to acquire an image represented by image data to be processed is discriminated in accordance with the identification points that have been decided. A color temperature that corresponds to the light-source type discriminated is set in a color-temperature setting circuit, and gray pixels having the set color temperature are extracted from the input image. White-balance correction coefficients are decided based upon the gray pixels extracted.