An image processing device includes an in-plane pattern detector that selects a pixel of interest in a frame image of interest, calculates in-plane correlation index values representing correlations between the pixel of interest and in-plane pixel patterns including the pixel of interest, and selects a most highly correlated pattern as an in-plane addition pattern. A reference pattern detector calculates inter-plane correlation index values representing correlations between the in-plane pixel addition pattern and reference pixel patterns in a reference frame image temporally adjoining the frame of interest, and selects a most highly correlated reference pixel pattern. A pixel adder adds the values of the pixels in the selected in-plane pixel pattern and the selected reference pixel addition pattern to generate a corrected pixel value, thereby achieving high sensitivity and a high signal-to-noise ratio under low illumination, with little loss of resolution.