The purpose of this study is to explore changes of problem solving processes by diagrammatic externalizations. Eighteen undergraduate and graduate students attempted to solve a complicated arithmetic word problem (the 100 yen problem). Fourteen subjects were allowed to write down their own ideas, while other four subjects were prohibited from writing any idea. We stated the differences of their performance and the problem solving processes, comparing both experimental results of the two groups. The results indicated that (1) the subjects improved their performance for solving the 100 yen problem by externalizations, (2) integrating multiple propositions was facilitated by externalizations, (3) externalizing diagrams made the subjects effectively construct propositional networks that were relatively free from specific structures of the given problem.