PURPOSE: To improve resistance to environments for built-in information by incorporating a conductive material produced based on the information into a nonconductive material, detecting the shape of the conductive material from outside, and reproducing the information.

CONSTITUTION: An information member 1 which is obtained by covering a conductive film having a shape accordant with the information with a nonconductive material, an electrode 2 which boosts the pulse obtained by an oscillator 7 and produces an electric field with the amplified pulse, an electrode 3 which detects the produced electric field are provided. In such a constitution, a mutual interference space is formed by the electrostatic connection between the end faces 14 and 13 of both electrodes 2 and 3. Then the information accordant with the shape of the conductive film is detected by the electrostatic shielding effect of the conductive film. Thus it is possible to obtain a system having high resistance to the environments with use of the non-visible information.