Abstract: Device for measuring the concentricity of the core 21 of an optical fiber 19 relative to a reference axis 22, comprising a means for determining the position of the intersection of the reference axis 22 with an optical face 23 on the end of the optical fiber 19, a means 17 for injecting light into the core 21 of the optical fiber 19, an objective 30 and a means 4 for observing, in a plane 5 conjugate with the optical face 23, the light emitted by the core 21 of the optical fiber 19, characterized in that the objective 30 has a numerical aperture sin ? smaller than the numerical aperture sin ? of the optical fiber to be measured.