An inputting unit 10 of a channel bandwidth utilization ratio evaluating server 1 inputs various traffic parameters and transmission parameters. A packet sending-out time computing section 21 obtains a packet sending-out channel time based upon a packet size and the transmission rate. Further, a probability computing section 22 obtains a channel bandwidth utilization ratio based upon the packet sending-out channel time, a cycle time of a packet, and a communication error ratio. Further, the channel bandwidth utilization ratio evaluating server 1 evaluates the obtained channel bandwidth utilization ratio. For example, the channel bandwidth utilization ratio evaluating server 1 determines whether or not receipt of a new call is permitted based upon the obtained channel bandwidth utilization ratio. Further, the channel bandwidth utilization ratio evaluating server 1 determines an optimum control based upon the obtained channel bandwidth utilization ratio.