To obtain a magnetic field measuring apparatus capable of accurately measuring a magnetic field, a magnetic field applying device capable of accurately applying a magnetic field necessary for a sample or a space and a magnetism shielding device for accurately obtaining an area of a zero magnetic field environment in the measuring apparatus for measuring an environmental magnetic field and the field generated from a substance or an organism.

A magnetic field detector 1 is installed on a polar surface (POS 2) of a superconductor 3 of a superconducting state, and reading of the magnetic field measuring apparatus at that time is set as a reference value. The magnetic field of the actual magnetic field measuring position is measured, and compared with the reference value to detect an absolute value of the magnetic field of the measured position.