Abstract: A user information storage unit stores user information associating, for each user, an electronic mail address and at least one location information piece of the user with each other. A registration unit generates a code for each user using the location information and electronic mail address according to a predetermined rule. An invoice information storage unit stores invoice information including the electronic mail address of a first user included in the user information. When receiving an access request for accessing invoice information from a second user whose user information is stored in the user information storage unit, the registration unit determines whether the first code of the first user matches the second code of the second user, and if the first and second codes match, grants the second user access rights to access invoice information generated by the first user and stored in the invoice information storage unit.