The aim of this study was to measure the effect of a group-based parent education program on parenting stress and attitude and comparing the same according to adult attachment styles.Twenty-two mothers who enrolled in the parent education program participated in our study. The participants filled in the Korean version of the Experience in Close Relationship Revised (ECR-R), Korean-Parenting Stress Index-Short Form (K-PSI-SF), Maternal Behavior Research Instrument (MBRI), and Symptom Checklist-90-Revised (SCL-90-R) before and after the program. We compared the pre-and post-scores of the groups and compared the differences in effect according to adult attachment styles.For all study participants, the Parent Distress (p=0.023) and Total Parenting Stress (p=0.018) significantly declined after the parent education program. There were no differences in other variables. Within the secure attachment group, the Total Parenting Stress (p= 0.008), Parent Distress (p=0.015), and Difficult Child (p=0.011) scores in the K-PSI-SF significantly decreased after participating in the program. The Difficult Child scores (p=0.040) significantly dropped in the K-PSI-SF post program within the secure attachment group, compared to the insecure attachment group.The group-based parent education program impacted parenting stress. Depending on the adult attachment styles, the effect of the program varied.