PURPOSE:To improve detection accuracy of tilt, height, etc., of a sample surface by imaging reflection light from a sample surface at a position of conjugate with a sample surface and by detecting tilt, height, etc., of a sample surface by casting the imaged light on the sample surface again to guide its reflection light to a photodetector and by detecting tilt, height, etc., of the sample surface based on information of interference fringes on the photodetector. CONSTITUTION:A reticle 9 is illuminated by an exposure illumination system 81 and its circuit pattern is imaged on a surface of a wafer (detection object) 4 on a stage 7 by a reduction lens 8. A surface detection system 2 detects and processes surface configuration information of a wafer. Object light 16 is cast on the wafer 4 at an incidence angle of 88 deg. and its reflection light and reference beam 17 are reflected by a mirror 19, reflected again by a mirror 22 through lenses 20, 21 to make them move reversely in the original optical path and reflected by a beam splitter 14 in a direction of prisms 23, 23'. The prisms 23, 23' enlarge a beam interval and provide a specified angle simultaneously to inject beam to a lens 24. Two beams projected from the lens 24 cross each other at a position A which is conjugate with a reflection surface of the wafer 4 and interfere there.