This study aimed in analyzing the Japanese language ability of the first year Japanese Literature students of Mahasaraswati University Denpasar, before and after the use of the Grammar Translation Method in Bunpou-Dokkai Level 4 learning and its effectiveness on students. This research is an experimental research with quantitative and qualitative approaches, using a one group pre-test and post-test design. The theories used in this research are behavioristic learning theory, the theory of morphosyntax that focused on conjugation of Japanese word clases and word order in sentences structures, and surface strategy taxonomy theory from Dulay et. al (1982). The results showed that the use of the Grammar Translation Method in Bunpou-Dokkai Level 4 learning can improve students Japanese language ability that can be seen from the increase in scores on the post-test. The average score of pre-test score was 45.6 and the average score of post-test score was 77.4. The N-Gain percentage was 60.11%. Based on N-Gain categories, this experimental study showed that the use of the Grammar Translation Method in learning Japanese language, especially Bunpou-Dokkai Level 4 learning was quite effective.