A biomagnetic measurement technique which can obtain a potential waveform corresponding to a ventricular muscle cell action potential in a non-invasive manner. The biomagnetic measurement apparatus including an operating circuit for magnetometer. The output data of the operating circuit for the magnetometer is collected and a current vector at time t is calculated. Further, an absolute value Ixy of the current vector, a potential waveform V (t) in time corresponding to depolarization of a heart from the absolute value of the current vector, and a potential waveform V (t) in a refractory period of the heart to a period corresponding to repolarization from the absolute value of the current vector are calculated.