A device and method of simple design for measuring displacement between a first part and a second part that are substantially coaxial, preferably mounted on one another by an annular linear link. The device includes a structure for mounting the device on the part, blades secured to the structure and bearing on an outer surface of an intermediate member, the member being mounted around the part, at least one strain/deformation sensor associated with each blade, the sensors configured to transmit output signals dependent on the levels of deformation of the blades, and a conversion unit configured to deliver, from the output signals, at least one datum corresponding to the relative position of the parts, preferably out of an azimuth angle, an elevation angle and an axial displacement.