A magnetic field distribution measurement device (1) provides a non-contact magnetic measurement on a subject's chest at a plurality of coordinates and forms therefrom time-series magnetic field distribution data. A first arithmetic device (2) in response generates image data representing a three-dimensional, intramyocardial current density distribution. A second arithmetic device (3) receives a plurality of tomographic image data separately obtained by a tomographic diagnosis apparatus and processes the data to generate three-dimensional, anatomical image data. A display device (4) receives these data and displays on an anatomical image an image representing an intramyocardial current density. Thus in a ventricle a lesioned or viable part of myocardium can be readily identified in location, size, geometry and level. Furthermore, the anatomical image may be replaced with an image representing a normal stimulation propagation circuit and serving as a template.