Although the Grand Justice Interpretation of No. 544 affirmed the constitutionality of the adultery offense, it is questionable if it still makes sense in reasoning. This study discusses the constitutionality of adultery offense from the viewpoint of limitation on the right to sex liberty against the humanity to justify the unconstitutionality of the adultery offense, in addition to criticize the reasoning of the Interpretation of No. 544. As a result, the study claims that adultery offense is not necessary to maintain the family institution.