A brain measurement apparatus configured to generate an MR image and a brain's magnetic field distribution of a subject includes: an MRI module having a transmission coil configured to transmit a transmission pulse toward the subject and a detection coil configured to detect a nuclear magnetic resonance signal generated in the subject by the transmission pulse; an optically pumped magnetometer configured to detect a brain's magnetic field of the subject; a generator configured to generate the MR image based on the nuclear magnetic resonance signal detected by the detection coil and generating the brain's magnetic field distribution based on the brain's magnetic field detected by the optically pumped magnetometer; a marker displayed on the MR image generated by the generator; and a helmet-type frame to which the detection coil, the optically pumped magnetometer, and the marker are attached and which is attached to a head of the subject.