This study investigates whether Facebook would be an "effective and easy" teaching tool in ESL classes in South Korean universities. Using a teacher's diary, action research was conducted. The study indicated that Facebook is not different from other new teaching tools; the teacher must familiarize him/herself with the tool to use it confidently. Second, a student's "lazy factor" is quite problematic in the learning process. Lastly, action research and a teacher's journal can increase teacher's self-accountability.