This paper reports our ongoing research on the development of diachronic legal terminology, which deals with temporal changes in legal terms. We started by compiling statutory corpora for them. Focusing on articles that define legal terms, we defined a set of regular expression rules. Our experimental result showed that we successfully extracted legal terms, their explanations, and their relations. Our terminology consists of 26,661 terms and 35,201 relations, in which the precision of the relations was 88.0\% with 100 samples chosen at random. Graphical output will enrich our understanding of the dynamics of legal terms
