A measuring device comprising a light source unit for projecting a pulsed distance measuring light, a projecting light optical system, a light receiving optical system for receiving a reflected pulsed distance measuring light, a light receiving part having a single photodetector, and a control unit for measuring a distance by measuring time from light emission of the pulsed distance measuring light to receipt of the reflected pulsed distance measuring light is disclosed. The light source unit has a plurality of light emitting sources arranged in a known relation and a driving unit for driving the light emitting sources at a predetermined time interval. The light receiving part has a reduced optical system arranged at position conjugate to the light emitting source for guiding the reflected pulsed distance measuring light to the photodetector. The control unit is designed to identify a photodetection signal by matching it with the light emitting source.