From the perspective of life span developmental psychology, which broadly grasps development as an issue of the entire life span, I am interested in measuring psychological well-being in a broad sense using self-reporting questionnaires. Precise measurements of the individual differences of psychological well-being and related concepts in the elderly during which human diversity blooms is difficult. The subject, however, is fascinating and challenging. In addition, what is an appropriate index for measuring psychological well-being and related concepts among older adults? Since we do not understand both the actual conditions and age-related changes of older adults, we must study and research “aged” across diverse domains from a life span developmental psychological perspective. Thus, we might find a key to resolve the issue of index for measuring psychological well-being.