A technique to provide an information-sharing system and the like is disclosed. According to this technique, there are provided an on-board information terminal to transmit one or more types of information among a vehicle information relating to user's own vehicle and on-board program information to acquire shared information, an area information acquiring system for acquiring area information, and an information-sharing server for calculating time function existing quantity based on time function according to one or more types of information among vehicle information and area information, calculates time function transmission quantity based on time function including the calculated time function existing quantity, arranges the calculated time function existing quantity and the time function transmission quantity to a corresponding position on a map, attaches the map information to the on-board program information, and transmits it to the on-board information terminal.