PURPOSE: To obtain a sensor device to be arranged at high density.

CONSTITUTION: A sensor element 1 or a sensor element group is formed of a cathode layer 12 and a cathode end connected therewith, and an anode layer 14 opposing thereto. Magnitude of current flow between the cathode end and the anode layer 14 varies depending on the field strength at the cathode end which varies depending on the gap (distance) between the cathode end and the anode layer 14. When the anode shifts toward the cathode end side, the field strength increases thus increasing the magnitude of electron flow correspondingly. Since the cathode 20 is formed by etching technology, it can be arranged at high density.