The purpose of this study was to construct the new Optimistic Attributional Style Questionnaire, and to examine its reliability and validity. For this purpose, two main inquiries were carried out. First, a preliminary questionnaire was given to 233 adults and 233 university students. Factor analysis yielded three factors, thus establishing three subscales. Following was an elaborated version of the questionnaire, i. e., the new Optimistic Attributional Style Questionnaire consisting of 23 items, and administered to 87 junior college students and 71 vocational school students. Its test-retest reliability coefficients with a three-month time interval ranged from. 63 to. 70, thus confirming its reliability. Correlational analyses with Yatabe-Guilford Personality Inventory proved validity in each subscale. The new Optimistic Attributional Style Questionnaire showed both its reliability and validity.