To provide a helmet for measuring an electroencephalogram by simply mounting, in which position can be easily adjusted.

The helmet 1 for measuring the electroencephalogram comprises a skin part 2 covering a head, a cushioning member 3 provided at the inside of the skin part 2, and sensor members disposed at a plurality of positions of the member 3 to measure the electroencephalogram in contact with a scalp 4. In this helmet 1, through-holes 7 each for sending compressed gas are respectively formed at sites corresponding to the disposing positions of the members 5, and jet holes 6 each for injecting the gas fed from the hole 7 to the head are formed at the members 5 to communicate with the holes 7.