This study was initiated to analyze previous findings on the ways to improve students' ability to solve problems and to explore the directions for the future studies in this area. To do these jobs, a model of problem-solving process was constructed based on the research in problem-solving, specially in the mathematical problem-solving, From this model, the meaning of problem-solving ability was deduced, That is, the problem-solving ability consists of conducting each subprocess of problem-solving successfully. And, several subject variables - ⑴ the knowledge needed to understand the problems and to devise the solution plan, ⑵ affective characteristics of the students(e.g., motivation, habits, beliefs about one's own ability etc.) that may affect the problem-solving process, and ⑶ managerial skill to control the process of problem solving-affect each subprocess. As one natural approach to improve the problem-solving ability, teaching heuristic was first tested for its effectiveness. The results have shown that the tendency to use heuristics is positively related with the problem-solving performance; recognizing the problem conditions where the heuristic is useful has contributed to the problem-solving performance. In addition to heuristics, teaching managerial strategy enhanced the problem-solving performance. However, there are still some students who have not learned heuristics successfully regardless of training. As potential ways to teach the heuristics more effectively, specifying the heuristics at finer level and analyzing tacit knowledge underlying the use of heuristics have been recommended.