In this presentation, I introduced the seven key concepts of "Discourse Politeness Theory", which explains that the actual impoliteness effects are caused by the discrepancy of estimations of the degree of "Face Threat" between speaker and hearer. Then, I analyzed several miscommunication cases in France and Belgium from the viewpoint of this theory. Finally, I discussed what is necessary in Japanese language education in Europe, in order to prevent misunderstanding and miscommunication related to politeness.The seven key concepts in discourse politeness theory are: (1) Discourse politeness, (2) Discourse default, (3) Marked vs unmarked politeness, (4) Marked vs unmarked behavior, (5) Discrepancy in estimations between speaker and hearer, (6) Politeness effect, and (7) Relative vs absolute politeness. According to this theory, "politeness effect" represents "perceived politeness from the viewpoint of hearer" and it is caused by the "discrepancy in estimations" between speaker and hearer of: 1) Discourse default, 2) The degree of Face Threat of a certain language behavior, and 3) Speaker's politeness strategies. There are three kinds of "politeness effects". 1. Plus effect, 2. Neutral effect, and 3. Minus effect.In the presentation, I theoretically analyzed several miscommunication cases in France and Belgium from the viewpoint of this theory.