The present invention provides a log data recording device which records log data concerning a processing of image data. The log data recording device includes a compression unit and a recording unit. If the image data is judged to be a pre-specified document image, the compression unit compresses the image data with a first compression ratio, the first compression ratio is different from a second compression ratio for compressing image data other than the pre-specified document image. The recording unit records the log data including the compressed image data.