A distance measurement device includes: a pulse light emitter that emits pulse light to a measurement target; an optical sensor that receives reflected light which is the pulse light reflected by the measurement target; and a controller that controls a light emission timing of the pulse light emitted by the pulse light emitter, and determines a distance to the measurement target, from a light reception timing of the reflected light detected by the optical sensor. The controller sets the light emission timing in each of N periods (N being a natural number less than K) selected randomly from continuous K periods (K being a natural number greater than or equal to 2) to a timing that is delayed by a random first time from a start time of the period.