Scanning rangefinder of simple, compact construction. The rangefinder is furnished with: an outer cover (1) in which a transparent window (2) is formed; a cylindrical rotary unit (3) inside the outer cover (1); a scanning/receiving window (4) provided in the rotary unit (3); a dual scanning/receiving mirror (5) disposed, angled, along the rotational axis of the cylindrical rotary unit (3); a motor (6) for rotationally driving the rotary unit (3); a disk part (13) arranged in the cylindrical rotary unit (3), anchored in an inside region thereof; a beam projector (14) anchored in a location where it is disposed slightly spaced apart from the rotational axis of the rotary unit (3); and a light receiver (16) anchored to, arranged coincident with the rotational axis of, the disk part (13) in the inside region of the rotary unit (3), and connected to a distance computation circuit (19).