An apparatus, method, and software stored on a computer-readable storage medium, for correctly reduce noise included in image data regardless of the characteristics of the image data. The noise reduction apparatus and method employ a determinator for determining whether a target pixel of image data corresponds to a flat portion, an edge portion, or a gradation portion based on a pixel value of the target pixel and pixel values of neighboring pixels of the target pixel; and a noise reduction unit for reducing noise included in the image data based on a result of the determining by the determinator.