This study examines the misuses of language which are overlooked during the ‘correction-activity’ sessions between learning partners in Tandem Language Learning. Misuses which were not corrected in the learning diary written in the target language by the learners were classified according to their respective situations. Following the classification, reasons for the misuses were analyzed. As a result, the most popular situation in which misuses were not corrected was the case in which misuses were understandable to both members of the learning tandem, regardless of the quality of the misuses. In addition, this study revealed that the language partners were not often aware of a distinction between spoken language and written language. Corrections by partners is very important in order to learn a language accurately. Appropriate guidance, in situations in which corrections of misused language is not taking place, is significant.