The aim of the research are: (1) to describe the types of errors made by students in pronunciation; (2) to find out the highest error frequency students made in pronunciation; and (3) to describe the factors influencing the students’ error in pronunciation. The method used in this research is a descriptive quantitative. This research was conducted at SMA Negeri 5 Surakarta in the academic year of 2018/2019.  The population of this research is the eleventh grade of SMA Negeri 5 Surakarta. The samples of this research are the XI IPA 4 which consists of 31 students. The instrument used to collect the data within this research is test. The data are analyzed by using error analysis procedure which consists of identifying students’ errors, describing the errors, explaining the errors, and evaluating the errors.
The findings of the research are: (1) The errors on mispronunciation made by the student are classified into two: segmental phonemes (vowel and consonant) and suprasegmental phonemes (word stress); (2) The percentage of each error is as follows: errors in vowel with the percentage of 63.21% or 598 errors of total 946 errors, errors in consonant with the percentage 27.16% or 257 errors of total 946 errors, and errors in word stress with the percentage of 9.83% or 93 errors of total 946 errors; and (3) The sources of error made by the students are divided into two types; interlingual error with the percentage of 78.44% or 742 errors of total 946 errors and intralingual error with the percentage of 21.56% or 204 errors of total 946 errors.
The study can be used by the teachers to know what kinds of errors which are often made by the students. The teachers can determine the best teaching method and technique to deliver the lesson in order to avoid the occurrence of errors. Besides, teachers can also find out what materials should be prioritized to reduce the students’ errors.
Keywords: error analysis, pronunciation, speaking skills