PURPOSE: To obtain a magnetometer having high resolution in which drift due to time or temperature is eliminated by arranging a coil for exciting resonance of spin and detecting the excited resonance, and a coil causing magnetic polarization in the vicinity of a sample made of a substance having resonant spin. CONSTITUTION: A coil 4 for exciting resonance of spin and detecting the excited resonance, and a coil 32 serving to generate a magnetic polarization field Hb along a predetermined direction and to compensate for a field Hlex are arranged in the vicinity of a sample 2 made of a substance having resonant spin. The polarization field Hb in the direction D is generated by the coil 32 and the axis thereof is perpendicular to the axis of the coil 4. The magnetometer comprises a phase shifter 34 and a high frequency signal is fed from a high frequency generator 6 to a balance mixer 18. Output voltage of a low-pass filter 20 is thereby varied and a field being applied to the sample is varied correspondingly. An electronic unit 36, a sample and hold circuit 38 and an integrator 40 are connected in the downstream of the filter 20 and a current is fed therefrom to the coil 32.