The objective of this research was to analyze students' mathematical-logical thinking ability. This research used the quasi-experimental method with randomized control group post-test only design. The sample of research was 82 students of the seventh grade which were chosen by using cluster random sampling technique. The experimental class, taught using problem-based learning approach with scaffolding technique, consisted of 40 students while the control class, taught using conventional

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... , consisted of 42 students. The research instrument was mathematical-logical thinking ability test. The findings showed that students in the experimental class had higher mathematical-logical thinking ability than those who were taught by using conventional learning. It can be concluded that problem-based learning approach with scaffolding technique had the significant effect on students' mathematical-logical thinking ability.