The present invention is to provide a home subscriber server configuration method and system that is accessible in switching to any one of plural HSS servers in a redundant configuration. Information stored in such plural HSS servers (e.g., HSS-A server 40A and HSS-B server 40B) are synchronized as identical information. When an interrogation for a particular HSS server to be accessed from the I-CSCF server 30 or the S-CSCF server 21 is received, the access information for the plural HSS servers 40A, 40B corresponding to the interrogation is returned after rearranging to the predetermined order of priority to the I-CSCF server 30 or the S-CSCF server 21 from which the inquiry is originated. If no response is received from either one of the HSS servers returned from the SLF server 50 within a predetermined time after the access or if no response is received to the resend operations, the I-CSCF server 30 or the S-CSCF server 21 selects the next HSS server from the plural HSS servers and gains access to such HSS server after switching thereto.