Measuring electrodes are disposed in positions T5 and T6 according to the international 10-20 system. Electroencephalographic data obtained from these measuring electrodes is received in an input portion, and converted into phase analysis data on a phase plane V-dV/dt by a phase analysis portion. By use of a set of feature parameters selected from an aspect ratio, a V-axis maximum value, a sub/total revolution number ratio and an RL/UB distribution ratio in a feature parameter calculating portion, a Mahalanobis distance is calculated in a Mahalanobis distance calculating portion. The abnormality of the electroencephalogram is judged on the basis of the Mahalanobis distance, and a result of the judgment is outputted.
Electroencephalogram diagnosis apparatus and method