Many electrodes are positioned inside a skull for obtaining several electric voltage variation wave information. A processing unit computes subtract operation between two neighboring electrical voltage variation wave information respectively and then can obtain electrical voltage difference waves. Furthermore, each electrical voltage difference wave is separated into a first band wave signal and a second band wave signal. After which, several first band wave envelope signals and second band wave envelope signals are obtained. It conducts a co-relation processing about the first band wave envelope signals and the second band wave envelope signals. So, a co-relation table is obtained for determining a position where an intracranial brain wave abnormality occurs. In this invention, a unique scientific approach to determine the spatial position of seizure onset occurred inside the brain. In addition, the position of intracranial brain wave abnormality can be concretized and visualized by the co-relation table.
