In the context of the emphasis on inquiry teaching in science education, this study looks into how pre-service elementary teachers understand and practice science inquiry teaching during field experience. By examining inquiry lesson preparation, practice, and reflections of pre-service elementary teachers, we attempt to understand the difficulties they encounter and what could result from those difficulties in their practice. A total of 16 seniors (fourth-year students) in an elementary teacher education program participated in this study. In our findings, we highlight three difficulties "on the lesson" that are related to teaching practices that were missing in the classrooms: (1) developing children's own ideas and curiosity, (2) guiding children in designing valid experiments for their hypotheses, (3) scaffolding children's data interpretation and discussion and another three difficulties "under the lesson" that are related to problems with the pre-service teachers' conceptualization of the task: (4) tension between guided and open inquiry, (5) incomplete understanding of hypothesis, and (6) lack of confidence in science content knowledge. Based on these findings, we discuss how these difficulties are complexly related in the pre-service teachers' understandings and action. Several suggestions for science teacher education for inquiry teaching, especially hypothesis-based inquiry teaching, are then explored.