1. An image processing device for processing a plurality of frame images which are temporally consecutive images, each frame image including pixels, the image processing device comprising: an in-plane pattern detector for selecting a pixel of interest from among the pixels in a frame image of interest among the plurality of frame images, calculating, for each of a plurality of in-plane patterns including the pixel of interest, an in-plane correlation index value representing correlation with the pixel of interest, and selecting, as an in-plane pixel addition pattern, on a basis of the calculated in-plane correlation index values, one in-plane pattern among the plurality of in-plane patterns that is most highly correlated with the pixel of interest; a reference pattern detector for identifying a reference pixel of interest, corresponding to the pixel of interest, in at least one reference frame image temporally adjacent to the frame image of interest, calculating, for each of a plurality of reference pixel patterns including the reference pixel of interest, at least one neighboring pixel neighboring the reference pixel of interest, or both the reference pixel of interest and at least one neighboring pixel neighboring the reference pixel of interest, an inter-plane correlation index value representing correlation with the in-plane pixel addition pattern, and selecting, as a reference pixel addition pattern, on a basis of the calculated inter-plane correlation index values, at least one reference pixel pattern among the plurality of reference pixel patterns that is most highly correlated with the in-plane pixel addition pattern; and a pixel adder for adding values of the pixels included in the in-plane pixel addition pattern and the at least one reference pixel addition pattern to generate a corrected pixel.