The purpose of this research was to describe the positions and causes of students' errors in algebraic thinking based on the cognitive style. This study was qualitative research with subject consisting of twelve students. The results showed that (1) students with Field Independent type tended to make errors at the stage of comprehension, transformation, and process skills while students with Field Dependent type tended to make errors at the stage of comprehension, transformation, process skills, and encoding; and (2) the causes of errors were the students' incomprehension that related to the purpose of the problem, the lack of understanding that related to mathematical modelling, the lack of students' accuracy, the students' inaccuracy of using knowledge to convert an equations to the equivalent equation, student's inability to calculate the solution of an equations, students deviated from the formula that they used before and the students' incomprehension that related to the unit of measurement in mathematics.