In one embodiment of the present invention, a significance test of pixel values is performed between a region where functions could be deteriorated in a disease-specific manner and a region where functions could be preserved even in cases of diseases using brain functional images. Then, the mean pixel value of the functionally preserved site is significantly greater than the mean pixel value of the functionally deteriorated site according to the significance test is determined as an a image including a neurodegenerative disorder. According to this embodiment, it becomes possible to objectively detect images of neurodegenerative disorders without using a database for healthy subjects.