To provide an authentication server, authentication program, and authentication system capable of referring to a database during updating work of the database and simplifying a synchronizing work of the database.

When an automatic synchronization processing means is active and a temporary local DB is valid (S30; Yes), an authentication processing means synchronizes user information of the temporary local DB with the outside (S31). Next, the authentication processing means refers to the user information, group information and hierarchy information in the temporary local DB (S32), refers to authority information in a local DB (S33), and calculates authority about a user (S34). When the automatic synchronization processing means is not active (S30; No), the authentication processing means synchronizes the user information of the local DB with the outside (S35). Then, the authentication processing means refers to user information of a local DB 20, group information and hierarchy information in a local DB 20 (S36), and authority information (S33), and calculates authority (S34).