In communication, we have to choose the expressions that we will use. There are several types of expressions in Japanesse. One of them is an expression for asking permission, includ the saseru grammar.The purpose is find out the errors and causes of the errors that affect the errors of expression for asking permission (saseru) in Japanesse. This research used a descriptive quantitative-qualitative method. The sample of this research is the students on second level of Japanesse Language Education Departement of Muhammadiyah University of Yogyakarta. In collecting the data, researcher used test and interviews techniques. The result of this research are the average value of 35 respondent is quite low in the assessment criteria. The errors of the respondents are in the grammatical aspect. This is because they prefer to answer using the “temo ii” sentence rather than the “saseru” sentence. The biggest factor of the respondents errors is Incomplete Application of Rules which is equal to 46.7% because the respondents failed to apply the language concepts of the target language