This study aimed to determine the difference in the improvement of students' mathematical representation ability in problem-based learning (PBL) and regular learning as well as to determine the difference in the improvement of  students' self confidence in PBL and regular learning. In addition, to find out whether there was an interaction between learning and students'  early mathematical ability toward the improvement of students' mathematical representation ability and whether there was an interaction between learning and students' early mathematical ability toward  students' self confidence. The population was all students of SMP Negeri 1 Lhokseumawe. The sample was taken randomly as many as 2 classes which were consisted of 60 students. Data analysis was conducted by using Two way ANAVA. The conclusion were (1) the ability improvement of mathematical representation of students given a PBL model was higher than students given regular learning. (2) the improvement of students' self confidence given a PBL model was higher than students given regular learning. (3) There was no interaction between the learning model and students' early mathematical ability toward the improvement of students' mathematical representation skill. (4) There was no interaction between learning model and students' early methematical ability  toward the improvement of students' self confidence. Keywords: Problem based learning model, regular learning, mathematical representation, and self confidence.