To provide the system where a call is bypassed against frame relay traffic congestion.

A frame relay termination circuit 2 of a frame relay exchange checks backward explicit congestion notification BECN bits in an address field format of a frame 8 received from a channel 10. When the number of frames whose BECN bits are set exceeds a threshold level within a prescribed time, it is discriminated that the channel is in congestion, a bypass signal 5 is sent to a control section 4. The control section 4 receiving the bypass signal 5 makes a call, whose connection is requested from a transmission frame relay terminal 6 to a called frame relay terminal 13, bypass through other channel 9 that is registered in advance so that the control section 3 bypasses the frame relay traffic on the occurrence of congestion.