PURPOSE: To send simultaneously a general packet while sending an immediate packet with priority in the inter-packet network (node) transmission control and to send the general packet even when plural immediate mate packets are sent

CONSTITUTION: Each packet node 1 is provided with an inter-packet network transmission control section 3 and the control sections 3 are connected in a ring by using parallel slot processing ring transmission lines 2. A transmission line utilizing rate detection circuit 13 detects a utilizing rate of the transmission line 2, and an operating slot control circuit 17 adjusts respectively each utilizing rate of an immediate packet and a general packet to be sent. Packets from its own node to the other node are divided into the immediate packet and the general packet and they are respectively stored in buffers 9, 10. A multiplex control circuit 12 and a multiplex transmission circuit 16 add a slot operating flag, a node address and a packet number to packets in the buffers 9, 10 as data of a fixed bit length and the data are inserted to an idle slot and outputted to the transmission lien 2.