Abstract: The present invention provides a filter device allowing unnatural variation in image quality caused by image processing to be suppressed. The filter device including a filter section performing a filtering operation on an input image data so that, when time-varying amount in a total frequency value in a neighboring-classes block configured with a couple of neighboring classes in a histogram distribution of the input image data is equal to or less than a predetermined value, time-varying amount of a frequency value in each of the classes in the neighboring-classes block is suppressed to be equal to or less than a predetermined limitation value.