Abstract: A device for optical measuring of small particles for analysis of the quality of the particles comprises a sample-feeding carrier which is adapted to take up particle samples in sample holders and transport the particle samples to a place for optical measurement, a mirror-supporting means which follows the movement of the carrier and has mirrors matching the sample holders, a device for illuminating a particle sample when positioned for optical measurement and a detector, which is sensitive to electromagnetic radiation and records at least one result of an optical measurement of the illuminated particle sample. A mirror of the mirror-supporting means reflects the particle sample, so that a mirror image thereof stands essentially still seen from the detector, when a measurement is being recorded, owing to the fact that the mirror image of the particle sample falls on a center axis of the movement of the mirror-supporting means.