Building the Taiwanese Learner Writing Corpus of Japanese and its Analysis: A Case Study of Japanese Subsidiary Verbs -teshimau Abstract This paper presents a description of how we build a corpus of written Japanese by Taiwanese learners and analyze errors focusing on subsidiary verbs –teshimau in Japanese. One unique design of the corpus is that we adopt a web-based access system, which enables researchers to access the corpus more easily without having to install any special computer programs. This research has been conducted with the financial support of the Sumitomo Foundation, fiscal 2005 grant for Japan-related research projects.