Apparatus for inspecting a surface of an object to be measured. The light source applies light to the surface. An objective lens opposite the surface receives reflected light. A light detector detects a component of the light incident on the lens from a direction parallel to its optical axis and obtains its light quantity. A slit is provided in the optical path between the objective lens and the detector in order to narrow the light detection extent in the surface to be measured. The surface condition of the object can be measured with a good accuracy independently of the shape of the object.
