Abstract: This paper describes an apparatus developed for the measurement of lubricating oil film thickness in an conformal contact. Lubricating hydrodynamic films were generated by a stationary micro-slider flat loaded against on a rotating transparent disc, and the minimum film thickness was measured by interferometry. The micro-slider flat was precisely polished with a high reflectivity, and the transparent disc was coated with semi-reflective Cr film. With a flexible slider holder, the slider flat can be positioned in such a way that a desired inclination with respect to the disc plane, that was a geometrical wedge, can be obtained and kept unchanged during operation. Using the test apparatus, lubricating films can be obtained under prescibed inclinations, loads, and velocities. The credibility of the measurement system was demonstrated by the good correlation between the experimental and the theoretical results. The test apparatus provides a new approach for evaluation of lunbricating films in conformal contacts.