PURPOSE: To improve the operating efficiency of a relay line while ensuring the communication quality without interruption of a call in the congestion state of the relay line in the ATM communication system.

CONSTITUTION: An ATM electronic exchange 10 consists of a cross connect device 30 used to provide a communication path being plural virtual paths to a relay line 400 and with an exchange device 20 used to connect a terminal equipment and the virtual path or between the virtual paths for each call. A call processing section 96 of the exchange device 20 selects a virtual path to be connected in response to a medium of the communication information and the attribute of the terminal equipment. A cross connect processing section 97 of the cross connect device 30 selects the virtual path without interrupting a call in response to the bypass priority and a bypass destination decided in advance for each virtual path at the congestion of the relay line.