選舉平等的保障，一直被視爲是現代民主的基本原則。在日本，則被規範於憲法之中。不過日本憲法並非只有保障一人一票而已，它還要求在政治過程中平等之實現，而此問題被稱之爲「議員定數不均衡」問題。特別是在二次世界大戰後之工業化，導致了都市人口增加，因而區域人口分配變得很不平均。爲此所造成的各選區選票價值差距的問題，形成了一項重要的憲法議題。自從1960年代起，此一問題也被多次地訴諸法院，而日本最高法院也針對參眾兩議院及地方議會分別作出了判決。本論文便是針對這些司法判決，試著從憲法的觀點去探討此一「議員定數不均衡」的問題。
The equal protection of election is considered as the basis of modern democracies. In Japan, it is regarded as a constitutional mandate. However, the Japanese Constitution does not only guarantee the principle of one person one vote, it also requires the realization of equality in the political process. This issue has been addressed in the reapportionment cases. Particularly the industrialization after the Second World War has resulted in an increase in the urban population, and the regional distribution of the population has become very unbalanced. The gross disparities in the value of a vote across constituencies have become a serious constitutional issue. Since the 1960s, this reapportionment issue began to appeal to the courts. The Supreme Court has delivered many decisions on this issue involving both houses of the Diet and the Local Assembly. This paper focuses on these judicial decisions and intends to study this reapportionment issue in Japan from the constitutional viewpoint.
