According to one embodiment, an image processing device capable of removing a horizontal streak that may show when a document is scanned and made into a file is provided. An image processing device according to one embodiment includes: an image processing unit configured to generate smoothing image data obtained by applying smoothing to image data, and save, as an image file, non-smoothing image data in which smoothing is not applied to the image data when a difference between the non-smoothing image data and the smoothing image data is equal to or greater than a threshold value, and the smoothing image data when the difference is smaller than the threshold value; and a storage unit configured to save the image file.