Photoelectric sensor for fraction automatic collector of liquid chromatograph which eliminates violation of the movable collector mechanism working rhythm, prevents liquid samples losses, excludes changes in fraction structures of the samples and pollution is described. The mentioned above benefits were gained due to replenishment of the unit with the industrial photoelectric sensor, which consists of the funnel with the through central opening, eccentrically located platform and a shaft with the longitudinal channel for the liquid to pass in the photoresistor plane and with the diametrically located window for the light bunch, coming from the lamp to the photoresistor, which signal is transferred to the movable mechanism.