1. A neurodegenerative disorders detecting apparatus that is capable of handling brain functional images, comprising: a processor; and a memory communicatively coupled to the processor when the apparatus is operational, the memory bearing instructions that, upon execution by the processor, cause the processor to perform operations comprising: defining, for the brain functional images, regions of interest in a functionally deteriorated site where functions could be specifically deteriorated in a neurodegenerative disorder to be detected, and a functionally preserved site where functions could be preserved even in said neurodegenerative disorder to be detected, respectively; and conducting a significance test using pixel values within the regions of interest defined for each of the functionally deteriorated site and the functionally preserved site, and determine that the neurodegenerative disorder to be detected exists when the mean pixel value of said regions of interest in the functionally preserved site is significantly greater than the mean pixel value of the regions of interest in the functionally deteriorated site.