The purpose of this study is to identify the pre-service teachers' the implicit theory of the happiness. For this purpose, 31 pre-service teachers were administered questionnaire consisted of the concept of happiness, the criterions for judging happiness and the factors related happiness. Using thematic analysis, first, the following themes were related to happiness: (1) social relationships(family, love, recognition, sharing, friendships, and giving, thanks,), (2) positive emotions(pleasure, satisfaction, and no difficulties or stresses), (3) self-determination and achievements, (4) gratification of physiological needs, (5) self-esteem, (6) healthy and (7) the purpose or life; the following themes were related to the criterions for judging happiness: (1) positive emotions(optimism and, satisfaction, no difficulties or stresses and composure, and thanks), (2) social relationships(family, caring, love and recognition), (3) competence and endeavor (4) self-confidence, (5) religion; the following themes were related to the factors related happiness: (1) optimism, (2) positive attitude, (3) caring, (4) self-esteem, (5) satisfaction, (6) endeavor and (7) thanks. It was recommended further researches appling the systematic approaches, such as deep interviews and analysis using factor analysis method.