PURPOSE: To facilitate the call of a telephone conference by accepting the change of a call destination telephone number and registering a telephone number after change on a telephone number data base.

CONSTITUTION: A telephone conference sponsor A registers telephone conference start time on schedule time data bass 1-3 in advance, and also, registers the telephone numbers of the sponsor A and telephone conference participants B-D on the telephone number data base 1-4 of a telephone conference command device 1. When the participant D is moved to another telephone set terminal 3-D', the participant D oneself re-registers the telephone number of a previous telephone set terminal 3-D to the telephone number of the terminal 3-D' by using the terminal 3-D' if it is before the telephone conference start time. The telephone number after change is registered on the data base 1-4 by accepting the change of the call destination telephone number from the sponsor A or the participants B-D. Thereby, the call of the telephone conference is easily performed.