大法官認定刑事法規有無違憲之虞的判斷原則其中之一為「罪刑相當原則」，然而「罪刑相當原則」具體的內涵為何，大法官並未給出具體的判斷標準。目前學界關心重點集中在量刑，以及「罪刑相當原則」的學理性概念。本文試圖以法益理論建立「罪刑相當原則」的具體判斷標準。首先本文將從分析日本兩次的強姦罪／強制性交罪的法定刑修改歷程，整理分析修法過程中的學說見解以及日本法務省下法制審議會的立法會議紀錄，從強姦罪／強制性交罪的法定刑修改過程中說明法益理論如何作用，接著導向法益理論的機能爭議。簡易說明法益理論如何從過去為刑法學中的通說見解到被揚棄，甚至認為立法目的已可完全取代法益理論的見解出現，但本文仍然認為法益理論在說明法定刑的決定以及法定刑的調整中具有決定性的作用。最後試圖從法益理論的觀點，提出「罪刑相當原則」的具體判斷標準。

One of the justice principles for judging whether a criminal law is in danger of unconstitutionality is the “principle of equivalent crime and punishment”. What is the specific connotation of the“principle of equivalent crime and punishment”? At present, the academic circles are more concerned about sentencing, and the rational concept of the “principle of equivalent crime and punishment” This article attempts to establish the specific criteria for judging the “principle of equivalent crime and punishment” based on the theory of legal interest. First of all, this article will analyze the revision history of the statutory penalties for rape/compulsory intercourse crimes in Japan twice, collate and analyze the theoretical insights in the revision process and the minutes of the Legislative Council of the Ministry of Justice of Japan. In the process of revising the penalty, it explains how the theory of legal interest works, and then leads to the functional dispute of the theory of legal interest. Briefly explain how the theory of legal interest went from being a general insight in criminal law to being discarded. Even the opinion that the legislative purpose can completely replace the legal interest theory appears, but this article still believes that the legal interest theory has a decisive role in explaining the decision of legal punishment and the adjustment of legal punishment. Finally, I tried to put forward the specific criteria for judging the “principle of equivalent crime and punishment” from the point of view of legal interest theory.