A signal processing device includes a preprocessing unit interpolating a G color component to positions of a pixel of interest and a pixel having the same color component as the pixel of interest so as to produce a first G interpolation signal; a proximity G pixel G color difference and R/B pixel producing unit producing a first R-G/B-G color difference signal on the positions of the pixel of interest and the pixel having the same color component, producing a second R-G/B-G color difference signal on a position of a proximity G pixel, and interpolating the R/B color component to the position of the proximity G pixel; a G color difference re-constitution processing unit re-constituting a third R-G/B-G color difference signal on the position of the pixel of interest; and a G color difference interpolation processing unit interpolating an R-G/B-G color difference signal to a position of a predetermined pixel.