In this study, we explored individual differences in insight problem-solving. According to the dynamic constraint relaxation theory (Hiraki & Suzuki, 1998), there are three sources of individual differences in insight problem-solving: the initial strengths of constraints, the evaluation of problem-solving attempts, and the learning rate that updates the strength value of each constraint. In order to validate the theory's predictions, we compared the subjects who could solve a geometric insight problem within 10 minutes with those who could not. A microscopic analysis of the solution processes and rating task revealed that the initial strengths of the constraints and the adequacy of evaluation are different between the two, but their learning rates are not. These results suggest that insightful problem-solvers try non-standard attempts more often even in the initial phase of their problem-solving and evaluate their attempts more precisely. The results were discussed in contrast with other approaches to insight.