PURPOSE: To obtain a tomographic drawing having good spatial resolving power and to achieve cost reduction, by extracting magnetic field component varying in the same phase from the magnetic field signals of both magnetic field direction sensors by a simultaneous signal measuring apparatus.

CONSTITUTION: Only the magnetic field 12 entering a pipe 7 from an opening part 5 is detected on the basis of Meissner effect by a magnetic field sensor 9. By extracting only the same phase component from the signals of the first and second magnetic field direction sensors 3, 4 using a simultaneous signal measuring apparatus 10, the intensity of the intersecting point P1 of the magnetic field detection directions of the first and second magnetic field direction sensors 3, 4 can be distinguished to be extracted. In the same way, when the second magnetic direction sensor 4 is rotated as shown by a dotted line to observe directions L2, L3, the signals of points P2, P3 can be distinguished to be extracted. By this method, the two-dimensional tomographic chart of the fine magnetic field of an examinee (living body) 13 can be drawn by a CT method accumulating the signals at respective points, that is, the output from the simultaneous signal detection apparatus 10 in the memory of a computer. Further, a three-dimensional chart can be drawn by moving the first and second sensors 3, 4 to a different surface along a rail 2 along with a frame 1.