PURPOSE: To reduce the recovery time from the congestion state by providing a congestion memory with congestion information representing whether or not an opposite connection destination exchange is in congestion set therein and referencing the congestion memory to decide an outgoing route immediately when each exchange receives a call and decides the outgoing route.

CONSTITUTION: Upon the receipt of a call, an exchange station selects an outgoing line path with respect to an incoming call to recognize a connection destination exchange station of the selected outgoing line. Then the exchange station investigates the congestion by inquiring about a congestion memory 25 based on the name of the exchange station recognized by a line selection section 26 selecting one line. The line selection section 26 checks a station name (e. g. B) by the congestion memory 25 and selects one of outgoing lines to be selected when no congestion is discriminated based on a code 0 of an information area. When the selected outgoing line is connected to a station name A, since the information of the congestion state is acquired, the line selection section 26 selects other bypass. Thus, the recovery time of the congestion state is decreased.