This study investigated learners of English as a foreign language (EFL) who engaged in a group discussion and saw how their discussion was affected by a preceding conversation with a chatbot. The chatbot was designed to reflect the Socratic inquiry method based on Eliza, a computer program developed for psychotherapy. Two case studies were conducted, and 130 university students (Case 1: n=63; Case 2: n=67) were divided into experimental and control groups and observed. Case 1 served as the pilot study and focused on the effects of a chatbot conversation on the discussion; the critical thinking, satisfaction, and number of conversations in experimental and control groups were analyzed. Case 2 examined the difference in critical thinking pre- and post-discussion in both groups. Case 1 showed that a preceding conversation with a chatbot might lead to an increase in the number of contributions that students made to conversations and could increase the number of conversations in which the students participated. Case 2 results showed that pre-discussion with a chatbot could increase the students’ awareness of critical thinking and enable them to form inquiring mindsets.