The purpose of this study is to estimate the longitudinal changes in anxiety of korean adolescents and examine the ecological factors on the changes. We applied the piecewise growth modeling to the KYPS data to analyze discontinuous changes. The results showed that piecewise growth function was most adequate to explain changes in anxiety in Korean adolescence in terms of the goodness of fit and meaningful interpretation. Adolescent’s anxiety was medium level at initial status, and maintained its initial level until College Scholastic Aptitude Test(CSAT), and had declined constantly after CSAT. Women’s overall level of anxiety was higher than that of man, and anxiety in vocational school students, after CSAT, diminished more slowly than in academic school students. And parental attachment, time varying covariate, had a negative influence on adolescent’s anxiety over the whole period of the data set.