1. A terminal device having the functions of receiving contents data from a server via a communication network, storing the received contents data in a recording medium, and updating contents hierarchical information stored in the recording medium with reference to overall hierarchical information so that the newly stored contents data is included in the contents hierarchical information, and wherein the contents hierarchical information indicates classified levels of contents data based on retrieval keys, and the overall hierarchical information indicates a hierarchical relation of the retrieval keys in the whole contents.