An information management method to be executed by a computer, the information management method includes; accepting (S101) a registration request that includes identification information of a mobile device, and position information of the mobile device that includes latitude and longitude; generating (S111) a value that includes the identification information followed by information that indicates a date and time when the registration request is accepted; storing (S 102) the position information in a first storage unit in a manner correlated with the value; generating (S121) another value that includes the information that indicates the date and time followed by the identification information; storing (S103) the position information in a second storage unit in a manner correlated with the other value; storing (S 104) the position information in a third storage unit in a manner correlated with the identification information; and storing (S 105) the identification information in a fourth storage unit in a manner correlated with the position information.