Abstract: The apparatus enables eddy current inspection of a metal tube having a thin layer on its outside face with magnetic or electrical characteristics that are different from those of the metal in-depth. The apparatus comprises a measurement head having a measurement coil (14) for surrounding the tube and means for powering the coil with voltage at high frequency, greater than 100 kHz, and for analyzing the impedance of the coil. The head contains a magnet (22) surrounding the coil and magnetic flux guides (24) on either side of the coil in the axial direction and co-operating with the magnet to constitute a magnetic circuit that creates a magnetic field whose maximum intensity lies inside the coil and close thereto.