1. A pattern discriminating apparatus comprising: a setting unit configured to set at least one area in a three-dimensional space in a three-dimensional image data; a feature value calculating unit configured to calculate a pixel feature value from one pixel to another of the three-dimensional image data; a matrix calculating unit configured to (1) obtain at least one point on a three-dimensional coordinate in the area which is displaced in position from a focused point on the three-dimensional coordinate in the area by a specific mapping, and (2) calculate a co-occurrence matrix which expresses the frequency of occurrence of a combination of the pixel feature value of the focused point in the area and the pixel feature values of the mapped respective points, and a discriminating unit configured to discriminate whether or not an object to be detected is imaged in the area on the basis of the combination of the specific mapping and the co-occurrence matrix and a learning sample of the object to be detected which is learned in advance.