1. An inspection apparatus comprising: a mounting system which mounts an object; an irradiation system configured to irradiate a substrate with light, wherein there is a film on a surface of said object and said mounting system changes the height of said object according to the thickness of said film; a first detection system configured to detect light from said object; and a second detection system which includes a first detection unit and a second detection unit; wherein: said first detection system is configured to detect a first mirror reflection light from the bottom of said film, and said second detection unit is configured to detect a second mirror reflection light from said bottom of said film; and a focal point for said first detection system is a cross point of a first signal from said first detection unit and a second signal from said second detection unit.