A method and an apparatus (1) are used to detect the position of the edge (2) of a moving product web (3). The apparatus (1) has piezoelectric elements (5), which firstly output ultrasonic pulses (10) and secondly pick them up and convert them into an electrical signal. The product web (3) is arranged between the piezoelectric elements (5) and a reflector (11) for this purpose. If the product web (3) is located in the measurement range of the piezoelectric element (5), it attenuates the ultrasonic pulses as a result of reflection or absorption during the double passage of the latter. The position of the product web edge (2) is calculated from this attenuation.