Abstract
This research was a descriptive research that aimed to identify the vowels that mostly mispronounced and the ability of third year English department students of Universitas Negeri Padang. This study also aimed to find out the factors leading to the students’ difficulties to pronounce English vowels. The sample in this study was K1 2017 class which consisted of 29 students selected by using cluster random sampling technique. The technique of data collection was pronunciation test that consists of 60 words and questionnaire that consists of 7 question. In analyzing the data, the researcher used Cambridge Advanced Learner Dictionary. From the result of the test, the researcher found that the common type of stress error that made by the students was vowel /æ/ (66.2%) from all the errors occurred. The mean of students’ level of error in English vowel was 66,1%.