Abstract: Apparatus for checking the tubes of a heat exchanger in an area spaced by a given distance from the end of said tubes, by means of a probe performing a helical movement, wherein the apparatus comprises a threaded rod, which can be screwed into a nut carried by a positioning and supporting device suspended on the exchanger tubes, first flexible means, which are perfectly rigid in torsion and of constant length ensuring the integral transmission of a rotation torque between the threaded rod and the probe, second flexible means ensuring the integral transmission of said rotation torque between the rotation control means and the threaded rod, a flexible sheath connecting the nut and a fixed chassis external of the exchanger, and means for sliding the assembly constituted by the probe, the first flexible means, the threaded rod and the second flexible means between a rest position in which the probe is placed in the said nut and an inspection position in which the threaded rod engages in the nut.