An object of the present invention is to provide a deterioration detection method of a head and a magnetic disk inspection apparatus in which the number of times of exchanging the head due to deterioration is decreased to improve the throughput of an inspection. In the present invention, a resistance value detecting circuit that is directly coupled to both terminals of an MR head is provided to measure the resistance value of the MR head, and the measured value is compared with the initial value of the exchanged head, so that it is possible to recognize a deterioration state of each head irrespective of a magnetic disk as a measurement target.