The purpose of this research is to find out students’ grammatical errors in their English speaking skill. The research question of this research is “what are the grammatical errors are made by students of English Education Department (EED) of Universitas Muhammadiyah Yogyakarta (UMY) in speaking.” The research was conducted in EED of UMY batch 2013. This research used quantitative research methodology. To answer the research question, the researcher used test to collect the data. The test was in the form of interview. In this research, there are four steps in analyzing the data; they are the determining the data, identification, classification and description. The result of this research shows that students made errors in omission, addition, misformation, and misordering. The total of errors are 125. In this research, the highest frequency of errors is omission where the students made 61 out of 125 errors. The second place is misformation. In this category, the students made 38 errors from 125 errors. The third place is addition. Here, the researcher found 24 errors from all. The last is misodering. It is the lowest of four categories which the researcher just found 2 errors from 130 errors.