To measure and compare noise under the same conditions by simultaneously measuring each induction noise of each equivalent impedance being connected to each terminal of a plurality of verification cables being provided in parallel while being separated from a noise-generating cable by a specific distance using a memory hicoder.

When a carrier wave is fed from an inverter to a noise- generating cable 2, a voltage is induced in a verification cable 1 due to an electromagnetic induction since the shielding effect of the verification cable 1 is not complete and a small voltage is generated between the terminals of an equivalent resistor 6 being connected to each cable. The each small voltage is simultaneously amplified at each channel of a memory hicoder 3 and output is displayed to a printer according to the range of each channel. More specifically, the induction voltage values of a plurality of verification cables 1 can be simultaneously detected.