PURPOSE: To attain a smooth traffic condition by regulating the input of packets when the number of continuous unit times having each disusing rate exceeding a level set previously exceeds the set number of unit times.

CONSTITUTION: A disuse rate calculation part 31 calculates a disuse rate showing the rate of disused packets to the packets included in a unit time. Then a disuse characteristic informing part 23 regulates the input of packets when the number of continuous unit times having each disuse rate exceeding a level set previously exceeds the set number of unit times. Thus the number of input packets can be decreased if a deteriorated state of the packet disuse rate continues for a prescribed period. Then it is possible to prevent a state where the packets are locally concentrated end to attain a smooth traffic condition.