DESIANA MATILDA ANUR Pengarang MARCELINUS YERI FERNANDEZ AKOLI Dosen Pembimbing 2 LENI AMELIA SUEK Dosen Pembimbing 1 Yanpitherzon Liunokas Ketua Penguji Marcelinus Yeri Fernandez Akoli Penguji 2 Leni Amelia Suek Penguji 1

The purposes of this research are to identify the types of grammatical errors made by the twelfth graders of SMAN 1 Poco Ranaka in constructing English passive sentences and to describe the possible causes of the errors made by the twelfth graders of SMAN 1 Poco Ranaka. This research used qualitative descriptive method. The subject of this research was 24 students from twelfth graders of second language program of SMAN 1 Poco Ranaka in the academic year 2022/2023. This research used test and questionnaire as instruments to collect the data. The researcher used three main steps, (1) observation (2) data collection (3) data processing. The result shows that there were four types of error made by the students. The errors were omission, addition, misformation, and misordering. The researcher also found three causes of errors made by the twelfth students such as carelessness, first language interference, and errors as a part of language creativity. Based on the result of this research, the researcher finds many students still did errors in constructing English passive sentences. Those errors are caused by the students’ have a lack understanding and motivation in learning passive voice. Keywords: Error analysis, Passive voice, Constructing, Twelfth graders