The present invention relates to a communication system, and the invention specifically provides a contents server that appropriately stores media contents from group users in a PoC Service and a conference service. The contents server includes: a recording unit that records media information from plural users in a communicatable state participating in a predetermined group, for each group; a detecting unit that detects a communicatable state or an uncommunicatable state of each participating user, at each predetermined time; and a deleting unit that deletes confirmed media information already recorded in the recording unit, upon detecting that all the participating users are in the communicatable state.