This paper presents a process model describing how a Kaizen team collectively creates innovation and improvement ideas for a production system and a protocol analysis approach based on the model. The process model captures the team-based creative problem solving practice as a process of updating a shared mental space comprising production system mental models (PSMMs) through exchanging utterances among the team members, where each utterance element characterizes an existing PSMM and/or creates a new PSMM. The paper also applies the proposed protocol analysis approach to an actual case, confirms its applicability and draws some insights into the process.