Mobile unit 16 which can activate Java-AP software obtains ADF 205 from IP server unit 13, receives SDF (security descriptive file) 204 by using ADF 205 from administering server unit 18 which a trustworthy organization (a communication provider which administers mobile packet communication network 15) administers, and obtains Jar file 206 by using ADF 205 from IP server unit 13. Then, mobile unit 16 installs Java-AP software containing these files. Java-AP, which is achieved by activating the installed Java-AP software, operates within the range of authorization expressed by policy information contained in SDF 204.