An automatic razor blade sharpener simultaneously sharpens and sanitizes multiple edges of a spring-loaded disposable razor blade cartridge without edge overheating by lubricated gentle contact of the blade edges with a moving rubber or polymeric compliant belt that is motor driven. The disposable razor blade handle is set in a cradle aperture, which is spring loaded against the moving belt. A sanitizing and lubricating liquid is dispersed from a container between the razor blade edges and the moving belt forms a thin liquid layer on the belt surface. The liquid layer is illuminated by transversely located light illuminator and the reflected light is received by a transversely located sensor. Deep grooves in the blade cutting edge reduce this reflection, indicating an overly worn blade. The absence of reflection actuates an LED, informing the user that the thin liquid film has evaporated or spilled out, or that the container lacks a sufficient quantity of sanitizing and lubricating liquid.