To provide a radiation disturbing wave measuring instrument, which accurately measures radiation disturbing waves generated by a radio device.

An input-attenuating circuit 2 attenuates the receive signal of an antenna 1A for disturbing wave measurement, and a carrier cancel signal generating circuit 10, which generates a carrier cancel signal, which has the same amplitude with and is opposite in phase to the carrier signal from the receive signal of an antenna 1B for carrier reception; and a wide-band coupling circuit 3, which cancels the carrier signal by putting together the outputs of the input attenuating circuit and carrier cancel signal generating circuit and a switch circuit 6 is inserted between the wide-band coupling circuit and a carrier cancel signal generating circuit, and turns off the switch when carrier intensity is measured, and turns off the switch when the radiation disturbing waves are measured. The output signal of the wide-band coupling circuit is inputted to a spectrum analyzer 5 via a low-noise amplifying circuit 4 to measure the frequency spectrum.