In this context, several recent studies have focused on the ability to understand a problem and difficulties regarding the solving as a means of improve students’ mathematical problem-solving abilities. Design of research explores types and factors of mistakes students in solving mathematical problems. The instrument used is problem solving test. Data from Indonesia secondary school students (N = 147) who were about 15 years old were analyzed using theory Newman. Procedure Newman includes: reading errors, comprehension errors, transformation errors, process skill errors and enconding errors. The results indicate to reading errors of 4.35%, comprehension errors of 17.39%, transformation errors of 34.78%, process skill errors of 23.91%, and enconding errors 19.57%. Factors errors students’ is not to absorb information well, not understanding the transformation of the problem, not following the material thoroughly, and comprehension mathematical of weak concepts.