PURPOSE: To effectively utilize an accumulation area by forming a mail obtained by adding a conference common identifier(ID) previously determined in common with plural conferences to conference material with its conference ID as destination information.

CONSTITUTION: The conference material for users of a conference terminal 110 are inputted from a material input means 114. The material is stored in a conference material storing means 112 and a conference ID for uniformly identifying the conference to be opened is applied to participator's conference material by a conference ID writing means 116. Then, the conference common ID to be assigned to all the conference services in common is applied as main information by a main destination writing means 113 and the mail information is transmitted to a center device 100 through a communication control means 111.