PURPOSE: To prevent erroneous connection due to the change of station information occurring when a switching processing is applied on a call storing the rewrite of the station information next by judging the rewrite of the station information only at the start-up part of the switching processing.

CONSTITUTION: When the change of the station information occurs during performing the switching processing, a station information change program is started up. The station information change program identifies whether or not a terminal or a trunk being processed at present exists, and sets a station information change flag on all the terminals or trunks being processed at present. After that, the station information is rewritten matching with a change request, then, the change of the station information is completed. In the switching processing, the change is always continued to be detected, and when the change is detected, and a content representing the detection of the change is transmitted to a switching processing start-up program, then, the switching processing is started up. The station information change flag of the terminal or the trunk from which the change is detected is referred in the switching processing start-up program.