PURPOSE: To prevent a card from being used illegally due to forgery of information, etc., by magnetizing one of two kinds of recording mediums, and thereafter, radiating a high frequency and forming a prescribed number of magnetic dissipation points, and allowing the other to execute write and read-out, based on this dissipation point information.

CONSTITUTION: When a card detector 11 detects the tip of a magnetic card 1, an AC signal generating circuit 23 generates an AC signal and supplies it to a magnetic head 12. As a result, a magnetic stripe 3 is recorded magnetically so that NS is varied in a prescribed period. In a high frequency radiating device 18, an oscillation control part 24 inputs a rotation detecting signal from a rotation detector 10 and counts its rotational signal, and allows a high frequency oscillator 26 to oscillate, whenever its result reaches a several pulse portion. This high frequency is led to a waveguide 28 and radiated from a radiating part 19, and a magnetic dissipation point P is formed in a part of the recording surface on the stripe 3. When a prescribed number of points P exist, the card 1 is issued, and at the time of use, it can be used only in this case, and read/ write of a magnetic stripe 2' are executed. When value information is gone, the contents of both stripes are erased.