PROBLEM TO BE SOLVED: To provide a brain function measurement apparatus capable of eliminating the need for large-scaled surgical operation during extended measurement, reducing the burden on a subject and a risk of developing an infection disease, and ensuring long-term stabilized measurement even when a failure occurs in the apparatus.SOLUTION: A plurality of electrode bodies 1 are attached such that the electrode bodies 1 penetrate the skull 102 of a subject 100, tips 12 are brought into contact with brain surfaces, and base parts 13 are exposed to the outside of the skull 102. A supracranial unit 2A, which is integrated with an electric circuit part 22 to communicate signals by radio with an extracorporeal unit 3 disposed outside the subject 100, is provided with contact parts 21 each coming into contact with the base part 13 of each electrode body 1 on the entire under surface thereof, and is fixed to the skull 102 in an easily detachable manner. In the event that leak of a hazardous liquid is caused by a failure of a supracranial unit 2A, the liquid will not reach the brain. When a supracranial unit 2A is exchanged, only a part of the scalp 101 needs to be incised by a simple operation no complicated operation is needed.
