The aim of this study was to investigate the moderating effect of adult attachment on the effect of job instability stress on burnout among office workers. The total of 355 cases participated in this study and only 352 cases of office workers were chosen for data analysis. The data was were analyzed using SPSS 23.0 program, descriptive statistic analysis, t-test, one-way ANOVA, Pearson s correlation analysis, linear Regression, hierarchical linear Regression. The result of this study are as follows. First, result of correlational analysis revealed that there were significant correlations among variables. Both job instability stress and adult attachment(attachment anxiety and attachment avoidance) were positively correlated with burnout. Second, adult attachment(attachment anxiety and attachment avoidance) showed a moderating effect on job instability stress and burnout. As the insecure adult attachment(attachment anxiety and attachment avoidance) increased, the effect of job instability stress on burnout decreased. This result can be understood as reducing the effect of job instability stress on burnout by focusing on work as an avoidant coping strategy when adults with unstable attachment experience job instability stress.