Distance measuring device and method for adjusting photodetection unit

The present invention provides a distance measuring device for measuring a distance, comprising a light emitting unit for emitting a measuring light beam toward an object to be measured, and a photodetection unit for receiving a reflected measuring light beam reflected from the object to be measured, wherein said distance measuring device comprises a gain control unit for changing photodetection sensitivity of said photodetection unit by a bias voltage and a light amount switching unit for variably changing a light amount of the light emitting element which emits the light beam toward the photodetection unit.