A distance measuring apparatus controls a forward laser beam to scan a detection area. A photodetector array includes a plurality of photo detecting elements. At least one is selected among the photo detecting elements as an effective element, and the effective element is changed from one to another in response to the direction of the forward laser beam. Identification is given of at least one among the photo detecting elements which receives an echo laser beam corresponding to the forward laser beam in a specified direction. An actual correspondence relation between directions of the forward laser beam and the photo detecting elements receiving corresponding echo laser beams is grasped on the basis of a relation between the identified photo detecting element and the specified direction. The selection and change of the effective element are executed according to the grasped actual correspondence relation.