This paper is a research report of France-Japan Collaborative Research about the Role of Conjectures in Problem Solving in Geometry. The purpose of this research is to clarify the effects of using the computer software Cabri-Geometry as a means of helping students who had difficulties in geometrical proof-problem solving. For this purpose, we made four didactical experiments in France and Japan. The subjects were the 9th grade students in France and 8th grade students in Japan. In conclusion, we clarified effects of using Cabri-Geometry as follows : (1) In both France and Japan, by using Cabri-Geometry in geometrical proof-problem solving, the students could gain "dynamic viewpoints of figures" and then could discover valid "procedures for proof' to solve the problems. (2) In France, the students could gain "visualization for geometrical figures" based on "dynamic viewpoints of figures" by using Cabri-Geometry. (3) In Japan, the students could gain a more impressivd "dynamic viewpoints of figures" by using Cabri-Geometry and could gain "changing viewpoints of figures" based on "dynamic viewpoints of figures".