An image processing device for eliminating or reducing block noise from an input image comprising a plurality of pixels arranged in a matrix to generate an output image, the image processing device comprising: specific area extraction means configured to extract a specific area comprising a target pixel from the input image; differential calculation means configured to calculate differentials between values of pixels in an image of the specific area extracted by the specific area extraction means, smoothing determination means configured to determine whether to perform a first smoothing process on the target pixel, on the basis of the differentials calculated by the differential calculation means; first smoothing means configured to, if the smoothing determination means determines that the first smoothing process is to be performed on the target pixel, perform the first smoothing process using a smoothing filter to smooth a value of the target pixel; and second smoothing means configured to, if the smoothing determination means determines that the first smoothing process is not to be performed on the target pixel, perform a second smoothing process using an edge-preserving smoothing filter to smooth the value of the target pixel, application determination means configured to determine whether to apply the result of the smoothing process performed by the second smoothing means, based on at least one of edge amount determination, texture determination or pixel value variation amount determination, pixel value selection means configured to select a pixel value smoothed by the first smoothing means or a pixel value smoothed by the second smoothing means as a pixel value of each pixel of the input image, wherein the image processing device generates an output image by replacing a value of each pixel in the input image with the pixel value selected by the pixel value selection means, and, wherein, the first smoothing process is a process of filtering the specific area, wherein the specific area includes a low-frequency component block, the second smoothing process is a process of smoothing the specific area while preserving a high-frequency component in the specific area. specific area extraction means configured to extract a specific area comprising a target pixel from the input image; differential calculation means configured to calculate differentials between values of pixels in an image of the specific area extracted by the specific area extraction means, smoothing determination means configured to determine whether to perform a first smoothing process on the target pixel, on the basis of the differentials calculated by the differential calculation means; first smoothing means configured to, if the smoothing determination means determines that the first smoothing process is to be performed on the target pixel, perform the first smoothing process using a smoothing filter to smooth a value of the target pixel; and second smoothing means configured to, if the smoothing determination means determines that the first smoothing process is not to be performed on the target pixel, perform a second smoothing process using an edge-preserving smoothing filter to smooth the value of the target pixel, application determination means configured to determine whether to apply the result of the smoothing process performed by the second smoothing means, based on at least one of edge amount determination, texture determination or pixel value variation amount determination, pixel value selection means configured to select a pixel value smoothed by the first smoothing means or a pixel value smoothed by the second smoothing means as a pixel value of each pixel of the input image, wherein the image processing device generates an output image by replacing a value of each pixel in the input image with the pixel value selected by the pixel value selection means, and, wherein, the first smoothing process is a process of filtering the specific area, wherein the specific area includes a low-frequency component block, the second smoothing process is a process of smoothing the specific area while preserving a high-frequency component in the specific area.