ABSTRACT This paper scrutinizes on transformation of the romantic love ideology in Japan. The ideology has characterized the modern family by uniting love, marriage, and sex (and therefore birth). The paper decomposes the ideology into two sub norms: the "love and marriage combination" norm and the "marriage and birth combination" norm. Still, these norms are yet to be quantitatively examined. So, data are collected in the 2015 Japanese National Survey on Social Stratification and Life Course (SSL-2015) with 12,007 respondents. They are asked whether they agree that love is indispensable for marriage and that marriage is so for birth. Results are shown as follows. (1) By distributions, about 80 percent agree with the both norms. (2) By comparing proportions, most young males and females relax the norms. However, young females tighten the "marriage and birth combination" norm. (3) As a result, by odds ratios, young males present consistent patterns on the two norms, while young females not. Therefore, mostly the romantic love ideology has been relaxed, but the "marriage and birth combination" norm survives and even revitalizes. This means that the ideology has been transformed and diversified, which may affect future forms of the family. These findings are obtained only in quantitative analyses.