1. An image processing device comprising: a noise reduction circuit that performs noise reduction processing on an image signal obtained by imaging of a subject image, wherein the noise reduction circuit includes a noise reduction filter configured to convert a pixel value of a pixel of interest through a calculation that uses the pixel value of the pixel of interest and pixel values of adjacent pixels included in a pixel block having the pixel of interest at a center, and the noise reduction filter is set, for the calculation, with a heavier weighting for vertically adjacent pixels that are the adjacent pixels located in parallel with the pixel of interest in a vertical direction than that for horizontally adjacent pixels that are the adjacent pixels located in parallel with the pixel of interest in a horizontal direction.