PURPOSE: To judge whether a person is the legally authorized one himself in such a state that the person moves, by taking out the brain wave measured form a close distance for one cycle to compare the waveform thereof with all of registered waveforms.

CONSTITUTION: The change of the magnetic flux of a brain wave measured by a measuring part 1 is converted to the change of voltage by a superconductor quantum interferometer 2 and the output thereof is amplified by an amplifying part 3 to be converted to digital signal by an A/D converter 4 while said signal is compared with the digital signal having a preliminarily registered waveform stored in a register file 6 by a comparing part 5. On the basis of the compared data, a judge part 7 judges whether two digital signals are the same or different. A person 9 to be judged enters a discriminating passage 8 and drain wave is measured to pass the discrimination at an outlet but, when he is not a permitted one, the lamp 11 provided to the upper part of the outlet lights to inform the abnormality. By the above mentioned constitution, the person to be judged receives judgement during the movement and the time required in identification is also short.