This study attempted to examine how group art therapy conducted at G, a professional social welfare institution in South Korea, affects low-income elementary school children. To this end, the Diagnostic Test for the Psychological Change Diagnosis test and PPAT (Person picking an Apple from a Tree) test were conducted as a pre- and post-test to confirm the change and to identify the meaning of group art therapy experienced by low-income children. A written interview questionnaire was collected, and a meaning unit was derived. For this study, the group of interest was low-income children in grades 4-6 in elementary schools nationwide, and from April 2021 to December 2021, a total of 477 students participated in at least 12 to 16 group art therapy sessions. The following study results occurred: First, in the psychological change diagnosis test, the score difference was statistically significant in all factors of self, peer relationship, and school life adaptation. Second, in the PPAT drawing test, differences in integration, problem-solving ability, high quality and internal energy, realism, and development stage scores were statistically significant. Third, what participants experienced in group art therapy was classified into four upper categories and 11 lower categories. Based on these research results, the significance and limitations of this study were discussed.