The aims of this research were (1) to find out the relative clause mastery of the
second students of SMK Purnama 2 Banyumas, (2) to find out the typical error
made by students
The method used was descriptive through test. The data were taken in August
2011 from the second year students of SMK Purnama 2 Banyumas. The number
of population was 150 students from six classes. The research took 27% of the
population as the sample of this research, which consisted of 40 students through
random sampling. After conducting, the research was relieved that An error
analysis in using relative clause of the second year students of SMK Purnama 2
Banyumas in academic year 2011/2012 was poor category because correct the
answer was 26.5%. It was found that the percentage of the students’ error was
75%. The errors made by students’ because they were still have difficulty in
understanding and mastery the language adequately and structure grammar rules
especially in using relative clause.