PURPOSE: To prevent the deterioration of service by setting the system in which the service state for each zone is calculated according to the arrangement state of each No. machine in the case when a No. machine in free state is generated and the dispersion waiting preference zone is determined.

CONSTITUTION: A monitoring means 101 for monitoring the system state of each No. machine A,B,C,..., service level detecting means 102 for detecting the presence of a No. machine in free state and the service level in each zone at that time, and a dispersion waiting instruction means 103 for outputting a dispersion waiting instruction for the zone having the lower level of service in preference are provided. The monitoring means 101 monitors the system state of each of machine numbers A,B,C,..., and when a machine number in free state is generated, the service level detecting means 102 calculates the level of service in each set zone, and the dispersion waiting instruction means 103 determines the zone in which the service level is inferior as the dispersion waiting preference zone, and the machine number in free state is put into disper sion waiting in that zone, and the speedy response to the call at a getting-on field is permitted.