A cable deterioration diagnosis device configured to diagnose deterioration of a cable having a plurality of electrical wires including one or more signal wires configured to transmit signals between a first device and a second device, and includes a test signal output unit configured to output a wave-like test signal to a test signal transmitting wire independent of the one or more signal wires among the plurality of electrical wires, a test signal extraction unit configured to extract a received test signal corresponding to the test signal from a signal propagated in a test signal receiving wire independent of the one or more signal wires and the test signal transmitting wire among the plurality of electrical wires, and a deterioration detection unit configured to detect the deterioration of the cable based on the test signal and the received test signal.