This study proves that the quoted legal text functions as the index which represents the contents of the text because of the characteristics of legal information, the automatic indexing in the secondary legal full-text databases can be possible without the assitance of the experts. In case of the establishment, amendment or repealing of law, change of words of index can be possible through revising the legal text quoted in the secondary legal full-text databases. Even when we dont input the full-text about retrospective documents, automatic indexing is also possible, and the establihment and the practice of expert knowledge and integrated databases are possible in case of the retrospective documents. This study indicates that it is necessary to have characteristic information the information experts recognize - that is to say, experimental and inherent knowledge only human being can have - built-in into the system rather than to approach the information system by the linguistic, statistic or structuralistic way, and it can be more essential and intelligent information system.