PHOTOSENSOR

PURPOSE:To conduct detection in a noncontact manner without being subject to the state of the surface of a body, and to detect the body with high reliability without producing dust by oppositely arranging a light-emitting element and a photodetector to the vertcal arm and front end section of the horizontal arm of an L-shaped package. CONSTITUTION:A light-emitting element such as a light-emitting diode 4 is disposed at the front end section of the vertical arm 2 of the package 1a of an L-shaped photosensor 1 and a photodetector such as a photodiode 5 at the front end section of a horizontal arm 3 so that a light-emitting surface and a light-receiving surface are faced oppositely through transparent windows 6. When the sensor 1 is mounted on the front end section of a supporter 8 and a wafer 10 placed on the hand section 9 of a robot arm is moved onto the horizontal arm of the sensor in the detection of the semiconductor wafer, an optical path 7 is interrupted by the wafer 10, thus detecting the wafer 10 by the photosensor 1.