The first array register stores neighboring pixels of the same color as the pixel of interest, which are sorted according to the size of the pixel value. The maximum signal comparison circuit compares the value obtained by adding the threshold ThB to the pixel value maxC, which is the (b1)th largest pixel value of the pixels in the first array register and the pixel value P22 of the pixel of interest. When the comparison shows that the pixel value of the pixel of interest P22 is larger, the pixel of interest P22 is determined to be noise, and the pixel value of the pixel of interest is replaced by maxC. The limit signal comparison circuit compares the pixel value P22 of the pixel of interest and the signal upper limit LB. When the comparison shows that P22 is larger than LB and is equal to or larger than maxC, only the pixel of interest is determined to be totally overexposed, and the pixel value of the pixel of interest is replaced by maxC.