1. A combing artifacts detection apparatus comprising: a feature-value calculating unit that calculates a feature value from an input image; a film-mode detecting unit that detects a film mode by using the feature value to obtain 2:3 pulldown sequence detection information and combination information of the input image; a pixel-difference calculating unit that calculates a pixel difference between fields and calculates, in pixel units, an absolute difference in luminance between relevant input images by using the 2:3 pulldown sequence detection information and the combination information; a luminance-variation determining unit that determines luminance variation based on a calculation result of the pixel-difference calculating unit; a combing artifacts-candidate detecting unit that detects continuous pixels, for which the absolute difference in luminance calculated by the pixel-difference calculating unit is equal to or larger than a first threshold, as a combing artifacts candidate per line based on a determination result of the luminance-variation determining unit, a number of pixels in the continuous pixels being equal to or larger than a second threshold, the combing artifacts-candidate detecting unit further detecting a line having the continuous pixels of a number equal to or larger than a third threshold as a combing-artifacts-candidate line; and a combing artifacts determining unit that determines that a combing artifacts occurs in the input image when the combing-artifacts-candidate lines detected by the combing artifacts-candidate detecting unit continue by a number equal to or larger than a fourth threshold.