A device for measuring the particle size distribution of sample material using light diffraction, comprising: a first light source for generating a first monochromatic light beam, the first light beam defining an optical path of the device; a first Fourier lens for the first light beam; a measuring cell having a sample chamber that is bounded on both sides thereof by windows (46, 48), for accommodating the sample material, wherein the sample material in the sample chamber can be irradiated with the first light beam in order to produce a diffraction pattern of the sample material when the measuring cell is arranged in the beam path of the first light beam; a detector means in the optical path for detecting the diffraction pattern produced by the sample material at angles in the forward direction; an evaluation means for determining the particle size distribution of the sample material on the basis of said diffraction pattern; wherein the length of the section of the optical path between the measuring cell and the detector means can be altered by a relative displacement between the optical path and the measuring cell such that the measuring cell can be arranged in the optical path at least at first and second measuring cell positions (13, 23) in order to be able to accommodate different particle size ranges; characterized in that the propagation direction of the first light beam is deflected by a reflector means so that the optical path is angled; wherein the first measuring cell position is located in the optical path upstream of the reflector means and the second measuring cell position is located in the optical path downstream of the reflector means; and wherein the relative displacement between the optical path and the measuring cell is effected transversely to the optical path at the first and second measuring cell positions (13, 23). a first light source for generating a first monochromatic light beam, the first light beam defining an optical path of the device; a first Fourier lens for the first light beam; a measuring cell having a sample chamber that is bounded on both sides thereof by windows (46, 48), for accommodating the sample material, wherein the sample material in the sample chamber can be irradiated with the first light beam in order to produce a diffraction pattern of the sample material when the measuring cell is arranged in the beam path of the first light beam; a detector means in the optical path for detecting the diffraction pattern produced by the sample material at angles in the forward direction; an evaluation means for determining the particle size distribution of the sample material on the basis of said diffraction pattern; wherein the length of the section of the optical path between the measuring cell and the detector means can be altered by a relative displacement between the optical path and the measuring cell such that the measuring cell can be arranged in the optical path at least at first and second measuring cell positions (13, 23) in order to be able to accommodate different particle size ranges; the propagation direction of the first light beam is deflected by a reflector means so that the optical path is angled; wherein the first measuring cell position is located in the optical path upstream of the reflector means and the second measuring cell position is located in the optical path downstream of the reflector means; and wherein the relative displacement between the optical path and the measuring cell is effected transversely to the optical path at the first and second measuring cell positions (13, 23).