Pronunciation plays a crucial role in effective communication. The incomprehensible pronunciation will lead to misunderstanding in communication. This present research is aimed to investigate the errors made by the students in pronouncing English vowels and the factors underlying the errors by using error analysis. This research was qualitative descriptive research and 15 students were involved as the participants. The data were collected through pronunciation tests and interviews. The results indicated that there were 615 total errors made by students in pronouncing English vowels which included diphthong (46.02%), short vowels (38.21%), and long vowels (15.77%). Besides, it was found that /??/, /?/, /e?/, /?/, and /?/ were the most frequently mispronounced sounds. The main factors causing students’ errors were intralingual transfer and interlingual transfer.

Keywords:  Pronunciation, Error Analysis, Vowels, Factors of Pronunciation Error