This research’s aim is to know error usage of juju hyougen by learner and its cause. This research according to the learners’ lack of knowledge about juju hyougen and its usage in Japanese sentences. The method that used in this research is combined methods, in other word mixed method, which mean this method uses qualitative and quantitave to acomplish the final aim. There is any reason why must uses mixed method, quantitave method used to counting the error type of juju hyougen usage, then qualitative method used to explain the cause of error that occured by learner. Researcher choose the whole people in PBJ UMY 2016 as research sample, because they should to be in intermediate japanese level since 3 years of study in university, and they ought to studied about juju hyougen before. Researcher uses paper test and questionnaire as intrument. The using of paper test was to learner’s knowledge about juju hyougen. Questionnaire’s function was to know the error caused by learner and to know thier struggle while answering paper test. Based on research’s result, there are many factor to cause error of using juju hyougen. First, there is language intevention while applying juju hyougen in sentences or conversation but this normal thing when studying foreign language. The second reason is the lack of knowledge, sample only studied it but not mastering and that is the most problem when learning about juju hyougen. this research was happen to help Japanese learner to understanding of error point when using juju hyougen and avoid it properly.