PURPOSE: To shorten time for computing a route by determining the optimum route between access and destination nodes for each connection request out of one or plural usable links selected in advance for each destination node positioned inside a network. CONSTITUTION: A packet exchange communication network is constituted by setting backbone nodes W-Z and local nodes A-E and these nodes are stored in a topology data base by a routing controller (a). The device (a) identifies the attributes of nodes from this stored information, determines the attributes of links 403 and 405 from the node attributes and constructs the matrix of links x nodes. The device (a) selects any link usable for destination node out of this matrix and concerning this link, a routing algorithm is calculated for each connection request. During connection time, the device (a) sends a data packet through an exchange to the destination node along with the previously calculated route. Thus, the time for calculating the optimum route can be shortened.