The purpose of this paper is to discuss more effective method of mathematical problem posing. We practiced such mathematical activities by students in high school (Grade 3). A feature of the method is to proivde situations in which students plan problems freely from the first. And another feature is to give students enough time to create problems. Actually, we report two practices of problem posing. In the first practice, some students had difficulty in making problem from the first, but many students were interested in considering around various problems and showed much originality in their problems. We observed the positive learning activities in problem posing, which might not be observed in the usual classes. In the second practice, many students were more interested in considering around various problems. We observed that many students got some deep understanding for the mathematical theories related to their problems and found that two practices of problem posing were more effective than one practice of that. Two practices show that opportunity in a class to discuss problems planned by students is very important in such activity.
