1. A medical image processing device, comprising: an input means for inputting brain image of a test subject; a segmentation means for segmenting gray matter tissue by performing a tissue segmentation process on the brain image of the test subject; a memorizing means for saving an image group of gray matter tissues of healthy subjects; an output means for outputting diagnosis support information based on statistical comparison between the gray matter tissue image of the test subject obtained by the segmentation means and the image group of gray matter tissues of healthy subjects; and a distinguishing means for distinguishing between normal and abnormal result of segmentation by the segmentation means, based on the voxel value of the gray matter tissue for the brain image of the test subject and per-voxel statistical value of the gray matter tissue for the brain image group for which the tissue segmentation process has been performed normally, wherein the distinguishing means distinguishes between normal and abnormal result of segmentation by the segmentation means by comparing the absolute Z-score of the voxel value of the gray matter tissue for the brain image of the test subject against a predefined threshold value.