This research proposed a guide that in essential in order to improve the GUI design of the postal self-service machine. From the result of the questionnaire investigation and the interview, we established tasks and performed a postal operating experiment. As the results of the experiment, it was confirmed that the GUI design of the existing postal self-service machine cannot offer suitable information for users, and the screen hierarchy cannot cope with the characteristic of postal service. A GUI design guidelines of postal self-service machine that is easier to be used was submitted, and a new GUI design was made and be evaluated
