In each node accommodated in a token-ring network system, a storage unit for storing priority levels is constituted by a plurality of flip-flops which provide bit positions of the same number as that of grades of the priority level. When storing a value of priority level which is higher than a value of priority level stored in the storage unit, the corresponding flip-flop of the storage unit is set. Two priority encoders connected to the output of the storage unit detect, from data of priority level stored in the storage unit, first and second priority levels and load then on registers, respectively. In accordance with the contents of the registers, the corresponding flip-flop of the storage unit is rest, when each node detects a value of priority level stored in the storage unit.