Magnetocardiogram (MCG) measurement using high-Tc SQUID magnetometers is receiving attention as a diagnostic technique for observing the electrical activity of the heart because the instrument is easy to operate and the liquid nitrogen coolant is low in cost compared with the liquid helium used in conventional SQUID magnetometers. In this study, we carried out MCG measurement on ten normal subjects and four patients with inferior infarction, using a 16-channal high-Tc SQUID in a prefabricated, magnetically shielded room. Using isofield contour maps of QRS waves at different times, we were able to locate the signal sources and observe their different variance in the normal subjects and patients with inferior infarction. The result shows that the method using a high-Tc SQUID magnetometer will provide assistance in the diagnosis of cardiac diseases.