A method for cleaning a test sample well, provided in a diagnostic test card, using a cleaning head having a cleaning tube delivering, at its free end, a cleaning fluid, and a suction tube mounted inside the cleaning tube for aspirating the contaminated cleaning fluid from its free end located in proximity to the free end of the cleaning tube. The method provides for relative displacement between the test card and the cleaning head, so that the test card occupies a cleaning position wherein the cleaning tube delivers, at its free end, the cleaning fluid to the inside of the well to be cleaned and the suction tube aspirates the contaminated cleaning fluid.