A device for measuring particle emissions of an internal combustion engine, in particular the soot concentration in the exhaust gas, has a signal transmission route, located between a transmitter and a receiver, which traverses a flow of exhaust gas carried in an exhaust gas tube of the engine. To avoid soiling of the active elements of the transmitter and receiver that would cause inaccuracies in measurement, the signal transmission route is embodied as a beam of light, which passes through two diametrically opposed openings in the wall of the exhaust tube. The light-admitting openings are each closed with a respective transparent disk. The disks are heatable and are heated to a temperature above the burnoff temperature of the particles. Appropriate light emitting and receiving elements are used in combination with appropriate heating and evaluation circuits which indicate the soot concentration and which control fuel input to change the soot concentration.