An apparatus for measuring light scatter, the apparatus having a light transmitter and reception optics for transmitting and detecting a light beam scattered in a measured zone, respectively, wherein an adjustment unit changes between a measuring mode wherein the optical axes of the light transmitter and the reception optics stand at an angle with respect to one another and intersect in the measured zone and a test mode wherein the optical axes of the light transmitter and the reception optics are parallel, wherein the light beam successively sweeps over the reception optics. The reception optics is rotatably held at a displaceable rotary axle, wherein the adjustment unit first rotates the reception optics about the rotary axle in the test mode until the optical axis of the reception optics is parallel with the optical axis of the light transmitter and then displaces the rotatable axle together with the reception optics.