This research aims at knowing the causes of students’ speaking anxiety and the dominant cause felt by the students. The subject of this research was second semester students of English Education Department of Universitas Muhammadiyah Purwokerto in 2017/2018 Academic Year. The number of students were 27. The type of this research was case study. This research used two kinds of method to collect the data; questionnaire from Santosa (2015) and interview. The participants were asked to choose the causes that make them feel speaking anxiety offered in the questionnaire items based on their personal opinion. The causes of speaking anxiety were divided into internal factors and external factors. Based on the questionnaire result, internal factors were 12% in the negative feelings and 9% in the opinion and beliefs. However, the external factors were 6% in other factors, 5% in classroom settings and activities, and 4 % of the teacher. The result showed that the major cause provoking students’ speaking anxiety was because they were concern more in grammar. It proved by the result of the questionnaire that 85.19% of respondents agree that they were anxious because they thought grammar is important in speaking. Therefore, they also still feel anxious because they are afraid of making mistakes in grammar and pronunciation. Hence, the students were less anxious because of the external factors; the classroom settings and activities, and teacher.