A group of participants taking part in an event is formed on the basis of intention of the participants. A grouping system includes a mobile terminal 3 having adjacent terminal communicating units 17, and a management server 1 for performing grouping. The management server 1 includes a member personal information database 51 for recording member ID information of the participants; an ID information combination database 52 for recording a combination of ID information obtained from another mobile terminal and ID information of itself; an event management database 53 for recording content of at least one event; an ID group management database 55 for registering an ID group; and group managing unit 67 for forming the ID group by linking ID information combinations having common ID information, recorded in the ID information combination database 52.