This study analyzed the use of fillers by learners of Japanese using the International Corpus of Japanese as a Second Language (I-JAS) in the following three aspects: (1) different usage across different learner proficiency levels, (2) different usage depending on the type of task, and (3) how filler usage differs between learners and native speakers. The results showed that beginnerlevel learners mostly used vowel-type fillers; usage of such fillers decreased as fluency increased, overtaken by vocabulary-type fillers. Furthermore, the study found that native speakers used different fillers in dialogue tasks than in individual monologue-style tasks, while beginner and intermediate learners showed no such tendencies, as such learners have limited knowledge of interjections and are unskilled in choosing different ones according to the type of task. While learners with a higher proficiency began to display differences in their use of fillers according to different tasks, they did not always accurately use these fillers.