To provide a height detection apparatus capable of detecting height information of a subject surface even in a narrow area, the height detection apparatus includes: an illumination optical system for illuminating the subject surface with a light flux emitted from a light source unit; an imaging optical system for causing the light flux reflected on the subject surface to form an image as a line image on an imaging surface; and a light detection unit disposed on the imaging surface. A light detection surface of the light detection unit is positioned in a plane rotated about a rotational axis, the rotational axis being an axis which is perpendicular to an optical axis of an optical element positioned optically closest to the light detection unit among optical elements constituting the imaging optical system, and is perpendicular to the line image to be formed by the imaging optical system.