A histogram stretching apparatus and a histogram stretching method are disclosed to enhance image contrast by stretching a histogram of an input image within a range of a preset maximum expansion level and a preset minimum expansion level. The histogram stretching apparatus performs proper stretching suitable for a characteristic of the input image in due consideration of a saturation portion and a distribution range of a histogram of the input image. The histogram stretching apparatus can improve stretching effects by removing the saturated portion of the input image, and can prevent image distortion even for a monochromatic image. The histogram apparatus can improve histogram stretching effects by adjusting entire image levels of an image having a histogram frequency distribution skewed to a dark or bright side before a stretching operation.