There is little research on the disillusionment associated with marital relationships among Japanese couples. The aim of this study was to develop a Japanese version of the Relationship Disillusionment Scale. The validity and reliability of the scale were examined. The scale was administered to 590 adults. Confirmatory factor analysis revealed that the Japanese version had a single-factor structure. Moreover, the scale had sufficient internal consistency, re-test reliability, and criterion-referenced validity. Furthermore, the scale distinguished married participants from divorced ones. Thus, the results demonstrated that the Japanese version of the scale has adequate validity and reliability among Japanese adults.