A distance measurement device includes: a mirror disposed so as to be tilted relative to a rotation center axis; a drive unit configured to rotate the mirror about the rotation center axis; a photodetector configured to detect reflected light, of laser light, reflected in a distance measurement region; and a condensing lens disposed on the rotation center axis and configured to condense the reflected light reflected by the mirror, on the photodetector. The mirror has a shape elongated in one direction and is disposed such that a short axis thereof is tilted relative to the rotation center axis in a direction parallel to a plane including the rotation center axis. A width in a short-axis direction of the mirror is smaller than a width of a lens portion of the condensing lens as viewed in a direction parallel to the rotation center axis.