An arrangement of the magnetic detection and excitation head has an excitation head with a U-shaped excitation core of soft magnetic material forming two legs, each having an end plane facing a surface of a measured object, and an excitation coil wound on the core excitable by a low frequency current; and a detection head with a rod-shaped detection core of non-magnetic or soft magnetic material and a detection coil wound thereon. An end plane of the detection core which is to be close to the surface of the object, and the end planes of the two legs of the excitation core are arranged such that the end plane of the detection core is between the end planes of the two legs and all the end planes are substantially on a common flat plane. Also, a position of the detection head relative to the excitation head is selected such that when an AC current of a predetermined frequency is supplied to the excitation coil, a selected one of a total induced voltage signal, which includes a voltage signal having substantially the same frequency as that of the supplied AC current and a Barkhausen signal induced into the detection coil, and the Barkhausen signal alone is detected.