An automatic white balance system according to an embodiment of the invention comprises a color separation and synchronization unit which has a line memory for generating a white-balance-adjusted YUV signal, a color judgment unit which judges whether or not a white balance adjustment is needed, a white balance adjustment gain computation unit which calculates a white balance adjustment gain on the basis of the result of the judgment at the color judgment unit and the white-balance-adjusted YUV signal, a reciprocal computation unit which outputs the reciprocal transformation value of the white balance adjustment gain, and a second multiplier which multiplies the white-balance-adjusted YUV signal by the reciprocal transformation value.