The present invention is to provide a memory rental service system in an intelligent authentication unit, the system allowing an application operating entity to setup or change any application freely and easily at a reduced cost of operating the application. In other words, the system is to separately lease one or more specific areas of a memory in the intelligent authentication unit (IAU) for independently authenticating personal identification such as fingerprints, to one or more operators who operate specific applications. A write API distributed to the operator is used to write the contents such as data or a program written in a specific area, while a read/write API is used to authenticate personal identification so as to read the written contents such as the data or program stored in the specific area and operate the application specified by the APL.