The purpose of the study was to investigate the total effect size of the domestic adult sandplay therapy, the effect size according to treatment variables such as the total number of sessions, the number of sessions per session, and the dependent variables such as psychological variable group, social variable group, and physiological variable group. To this end, 19 related academic journals and master's and doctorate thesis were selected from 2000 to 2020, and a total of 166 effect sizes were calculated. As a result of the study, the overall average effect size was.749, which was the medium effect size and was statistically significant. As a result of the analysis of the effects according to the treatment variables of the effect size per the total number of sessions was found to be most effective in the 12-session program, and the effect size in line with the number of sessions per week, was described as a medium effect size for both one session and two sessions, but the difference in the effect size was not statistically significant. In terms of the effect size for hours per session, 60 minutes was the most effective. As a result of analyzing the effect of the dependent variables, the effect size of the psychological variables was found to be the most effective. This study proved its effectiveness by conducting a meta-analysis study on sandplay therapy for adults in Korea, and it is meaningful that treatment variables and the dependent variables should be considered when constructing sandplay for adults It is also meaningful in that it provided practical data on the need and development of sandplay therapy to improve mental health and sociality, and physiological changes of adults at psychological counseling and treatment sites.