The purpose of this study was to examine the effects of collaborative reflection aimed toward teacher knowledge development. To accomplish this purpose, we recorded and analyzed collaborative and reflective discussions that were held by student teachers who had practiced simulated classes of elementary school science. The records of their discussions were analyzed with respect to both the unit of utterance and the discussed topic. The results of the analysis showed that, from the viewpoint of the utterances, both the “discovery of problems” and “solution of problems” could be performed. However, discussion related to the complex knowledge areas was not performed so much, and the highest ratio was occupied by utterances categorized as teaching acts. On the other hand, the analysis of topics indicated that student teachers could reflectively discuss their classes with respect to not only teaching acts but also other knowledge areas, and they often considered learners’ points of view. From the above results, collaborative reflection was concluded to be effective as a strategy for teacher knowledge development.