There is a growing awareness of the so-called "Shadowing" among English teachers in Japan. "Shadowing" is now believed to be one of the most effective and pragmatic methods to improve learners' English speaking ability. This paper reports an attempt to improve the third-year students' English proficiency by means of "Shadowing Method" using CALL system. The results shows that the method helped some of them improve their shadowing skills ; however, there still remained a question why it did not help the others. Therefore, in this paper, its possible causes are to be analyzed.