In this paper, a line-laser-based yarn break sensor is proposed. In the proposed sensor, yarns are illuminated by a line laser placed on one side of the yarn plane. A screen is placed on the other side and the image formed on the screen is detected by a camera. The total number of yarns is compared with the total number of shadows formed by the yarns or the total number of light spots formed due to the distances between yarns. If the total number of yarns to be detected is greater than the total number of shadows or light spots formed due to the distances between the yarns, the sensor warns of breaking. In the proposed method, evaluation is made using only light spots or shadows formed by the yarns. Consequently, the yarn type, structure, color, or dimensions do not affect the results.