The purpose of this study is to develop and apply a problem-posing program for elementary school students according to the degree of structure of task situations in the area of geometry and measurement, and to compare its effectiveness to provide implications for problem-posing instruction. In the process, changes in brain activity were analyzed together to verify the effect of the problem-posing program on the brain and provide empirical evidence. For this purpose, the experimental group performed the problem-posing program in an unstructured situation and the control group performed the problem-posing program in a structured situation for 8 sessions, and evaluated the change of abilities in problemposing made by students during the class according to analysis framework. We found that the students further developed their problems following the learning steps in the problemposing program. In particular, the experimental group showed higher improvement in the level of problem-posing and showed significant activation on the brain areas: the frontal regions, the right VLPFC area, and the DLPFC area. These results suggest that it is necessary to increase the reflection of problem-posing tasks in unstructured situations in the curriculum, develop and apply various task types, and present systematic learning steps together.