An image processing unit is disclosed that smoothens a notice pixel of input image data with pixel values of pixels around the notice pixel to reduce noise in the image data. The image processing unit includes an edge extraction unit that extracts an edge based on the pixel values of the image data; a region determination unit that determines a region to be processed where a sum of edge intensities of the pixels including the notice pixel becomes greater than or equal to a threshold; and a smoothening unit that changes a smoothening intensity in accordance with a size of the region to be processed to smoothen the notice pixel corresponding to the region to be processed.