PURPOSE: To reduce a data transmission time by connecting a call with higher priority with a path of a short distance without selecting a 2nd path or a 3rd path or the like whose transmission distance is longer.

CONSTITUTION: An operating state (an operating rate and a call to be connected with high priority) of each of relay lines 41,42,43 is stored in call control memories 31,32,33 of data exchanges 11,12,13. A terminal equipment 22 sends a call packet including a high priority designation signal to a terminal equipment 24. The data exchange 11 compares the priority added by the caller terminal equipment 22 with the operating state of the relay line 41 making a connection request for each call based on a rate table of the call control memory 31 and when the priority of the terminal equipment 22 is high and the relay line 41 is in congestion, the data exchange 11 bypasses automatically a call communicated between the terminal equipment 21,23 with low priority to the relay line 42 to connect the terminal equipment 22,24 having a call with high priority through the relay line 41 of a shortest distance.