Magnetism generated in the cervical or waist part of a subject is measured without the neck or waist of the subject being bent forward. A sensor cylinder is arranged to have a four-sided cylindrical shape. One side at the distal end of the sensor cylinder is moderately curved. This allows the side at the distal end of the sensor cylinder to come into direct contact with the cervical or waist part of the subject when the neck or waist remains not belt forward, whereby a faint magnetism generated in the spinal cords or nerves of the subject can favorably be measured.
