A distance measurement apparatus comprises a distance measurement optical signal generation part, a collimating part, a beam diameter change part, an emission direction control part, and a beam diameter change control part. The distance measurement optical signal generation part generates an optical signal for measuring the distance to a target. The collimating part collimates the optical signal. The beam diameter change part is able to change a beam diameter of the collimated light. The emission direction control part controls an emission destination of the collimated light with the diameter changed. The beam diameter change control part controls the changing of the beam diameter by the beam diameter change part according to the emission direction of an outgoing.