This study aimed to investigate the effect of positive psychology art therapy on the subjective well-being of siblings of children with developmental disabilities. A notice of the recruitment of participants in a group art therapy program was posted at a welfare center. Of those who voluntarily decided to participate, seven children who met the criteria were selected, and two groups were formed. Group A consisted of three persons and group B consisted of four persons. Eight sessions of the program were conducted once a week, for 90 minutes. The researcher wrote progress notes and tests of subjective well-being were conducted. According to the quality analysis, participants who initially had difficulty exploring and expressing emotions were able to resolve negative emotions, feel positive emotions, and experience the purification of emotions as the sessions progressed. It also became an opportunity for participants to discover and enhance strengths in themselves, their families and others, thereby creating positive resources to help participants grow. As a result of an assessment through a non-parametric test Wilcoxon signed rank test, it is judged that positive psychology art therapy has positive effects on the sub-factors of subjective well-being, including positive efficacy well-being, positive affective well-being, and negative relatedness well-being. The results are meaningful in that they support the efficacy of positive psychology art therapeutic intervention for siblings of children with developmental disabilities.