The primary objectives of this study were to identify who is happier in workplace. To do this,this study proposed and analyzed a theoretical model consisting of demographic factors such as sex differences, age band, marital status, child quantity, religion, education level, position, job, income etc, psychological factors such as extroversion, neurosis, positive belief and happiness level. The major results of analysis reveal that first, both demographic factors and psychological factors have a positive effect on the happiness level of office-worker. Second, child quantity, neurosis and positive belief is an important factors in predicting office-worker's happiness. In conclusion, the implication of our research is to verify factors to promote the happiness level of office workers