A method monitors a circuit breaker in an electrical power supply network, in which one section of the electrical power supply network is monitored in respect of the occurrence of a fault. Upon detection of a fault in the monitored section, a trigger signal is output to a circuit breaker bordering the section, and a switch-fault signal indicating a fault upon opening the circuit breaker is generated if a continuous current flow through the circuit breaker is detected after the trigger signal is output. In order to provide for a preferably rapid and reliable detection of a continuous current flow or an interruption of the current flow during the monitoring of a circuit breaker, it is provided that a curve shape of the time curve of the instantaneous current flowing through the circuit breaker is investigated in order to detect a continuous current flow.