Magnetic field measurement method and magnetic field measurement apparatus

A magnetic field measurement apparatus in which a first direction, a second direction, and a third direction are perpendicular to each other, the apparatus comprising:

• a light source that emits light;
• a medium through which the light passes in the third direction and that changes optical characteristics depending on a magnetic field of the measurement region;
• a photodetector that detects the optical characteristics;
• a first magnetic field generator that applies a magnetic field in the first direction to the measurement region;
• a second magnetic field generator that applies a magnetic field in the second direction to the measurement region;
• and
• a calculation controller that causes the first magnetic field generator to generate a constant magnetic field with a first level on the first direction side and a constant magnetic field with a second level on the first direction side as the magnetic field in the first direction, causes the second magnetic field generator to generate a constant magnetic field with a first level on the second direction side and a constant magnetic field with a second level on the second direction side as the magnetic field in the second direction, and calculates the magnetic field of the measurement region using a detection result from the photodetector, the magnetic field in the first direction, and the magnetic field in the second direction.