1. A biomagnetic measuring system comprising: a plurality of magnetometers, each being disposed two-dimensionally at a position of (x, y) coordinates in parallel to the chest surface of a living body and used for measuring a time change of a magnetic field component in a z direction vertical to an xy plane of a biomagnetic field to be generated from the living body or time changes of magnetic components in both x and y directions in parallel to the xy plane from two opposing directions; a calculating device for calculating an output signal from each of said plurality of magnetometers used for measurements in the two opposing directions; and a display device for displaying a result of the calculation; wherein said calculating device performs: (1) calculations to obtain current distributions in the two directions from the output signals and/or to obtain distributions of the amplitudes of those current distributions; (2) a calculation to obtain an isointegral map according to the output signals in a predetermined period, and to obtain a region having an isointegral map value exceeding a predetermined threshold value; (3) a calculation to estimate the amplitude, direction, and position of one current source, from the output signal at a predetermined point of time; (4) at least one calculation selected from the calculations to obtain current distributions in the two directions at the predetermined point of time and to obtain distributions of the amplitudes of those current distributions, assuming the amplitude, direction, and position of the one current source; (5) a calculation to convert data so as to determine an optimal position for displaying the data that represents a three-dimensional heart model simulating a heart shape, and current distributions in the two directions and/or distributions of the amplitudes of those current distributions obtained in the calculation (1), using the result obtained from at least one of the calculations; (6) a calculation to adjust the base levels of current values into one with respect to the position-adjusted current distributions in the two directions and/or distributions of the amplitudes of those current distributions; and (7) a calculation to obtain synthesized image data obtained by projecting the base-level-adjusted current distributions in the two directions and/or the distributions of the amplitudes of those current distributions, from the z direction, on a position denoted by the (x, y) coordinates of the data representing the three-dimensional heart model, and wherein the synthesized image data is displayed two-dimensionally or three-dimensionally on said display device.