A data processing apparatus is provided for processing an image signal obtained from a solid-state image pickup device, in which a plurality of types of color filters are discretely provided on pixels, and a pixel to be interpolated and surrounding pixels thereof have image signals. The apparatus comprises an interpolation section for generating a missing color signal in the image signal of each pixel by interpolation using at least the image signals of the surrounding pixels among the image signals of the pixel to be interpolated and the surrounding pixels thereof. The interpolation section obtains an interpolation pattern, which is similar to a pattern of data values of the pixel to be interpolated and the surrounding pixels thereof, depending on uniformity and gradient of the image signals of the pixel to be interpolated and the surrounding pixels thereof, and performs interpolation depending on the interpolation pattern.