In this study, the effect of shadowing training on advanced learners of Japanese as a second language was examined. Specifically, we aimed at answering the following: (1) What kind of changes could be observed in the learners' ability by measuring seven language fields and three cognitive fields attributed to a month-long shadowing training? (2) What kind of changes could be observed in the subjects' performance in shadowing after a month of training? Findings show that change was observed in dictation and in repetition via language evaluation; and change was also found in the listening span test via cognitive evaluation. Furthermore, changes were seen in the average of utterance rate value and reproduction rate in the subjects' performance in shadowing. To conclude, a month-long training in shadowing leads to: (1) the improvement of abilities in written and oral production, and the expansion of working memory capacity through auditory presentation; (2) an improvement in fluency and accuracy in the subject's performance in shadowing during the fifth day of the first week of training compared to the first day of training.