A failure handling system capable of performing failure notification and shutoff control, thereby improving network operability. When failure is detected, an outgoing frame shutoff controller performs shutoff control on the local device such that the local device stops outputting communication frames to a receiving client device. A failure notifier notifies a network manager that the failure has been detected. On receiving a shutoff command, an incoming frame shutoff controller performs shutoff control on an originating client device such that the originating client device stops outputting the communication frames. A communication route manager manages communication routes through which the client devices communicate with each other across the network. On receiving a failure notification from a first transmission device, a shutoff information sender looks up the communication routes to identify a second transmission device connected with the originating client device, and sends a shutoff command to the second transmission device.