The electrical activity of the human heart and brain are noninvasively visualized and analyzed using a multi-channel superconducting quantum interference device (SQUID) system. Multi-channel SQUID systems for magneto-cardiogram (MCG) and magneto-encephalogram (MEG) procedures have been developed by improving SQUID and cryogenic technology. Recently, we have developed two types of biomagnetic systems. The SQUID system, which utilizes a low-temperature superconductor (LTS) SQUID, is capable of detecting very weak signals, because the magnetic sensor is sensitive to signals above a few fT/ (Hz)1/2; this enables even fetal heart disease to be detected within the system's scope. A specially developed display method eases the estimation of distributed current sources. Abnormalities in the current distribution for an ischemic heart and propagation pathway for an arrhythmia are thus easily detected. Moreover, cortical functional abnormalities in patients with chronic dizziness can be visualized. A high-temperature superconductor (HTS) SQUID device system is under development as a next-generation product. The device system is designed to save space and provide mobility for the overall system, including the magnetically shielded cylinder. Due to an improvement in HTS-SQUID sensitivity and the introduction of a noise reduction technique, the real-time measurement of cardio-magnetic fields has become feasible.