A community server categorizes and accumulates messages exchanged by users on a virtual community for respective topics. The community server includes a subscription type setting unit, which provides, to each user and predetermined administrator, a mechanism for selecting a subscription type indicating the way each user subscribes to messages posted to the virtual community. For this purpose, the subscription type setting unit manages the subscription types of respective users for each community using a subscription type table of community management information, and changes the subscription type in the subscription table in accordance with a request from each user and administrator.