The invention relates to a gas bubble sensing device (1) for sensing gas bubbles in a liquid. In order to provide a reliable detection of inadmissible gas bubbles at minimum cost and required installation space, the invention provides that the gas bubble sensing device (1) comprises two ultrasonic emitters (2, 3), which are both connected to one ultrasonic signal generator (10) in a signal transmitting manner.A gas bubble sensing device senses gas bubbles in a liquid. The gas bubble sensing device comprises two ultrasonic emitters, which are both connected to one ultrasonic signal generator in a signal transmitting manner. Further, the gas bubble sensing device comprises two control devices that are each connected to one of the signal processing devices in a signal transmitting manner, wherein one of the control devices comprises an output port, at which it provides a synchronization signal during operation.