This study aims to the professional growth of elementary science teacher on Problem-based Learning designed by collaborative inquiry. This study uses the case study methodology with natural science teachers (cooperation between teachers) in an elementary school in TaoYuau County as the object of study. The period time of study covered two semesters a whole year, and there were three classes a week. The researcher and cooperative teacher jointly develop three PBL teaching units in the upper semester, then they did teaching observation in the next semester. Through the whole study process, cooperative teacher had changes in professional development in the full year. The research tools were:「"PBL design evaluation table", "PBL review views table", "PBL teaching design evaluation table", "teachers' professional development self-evaluation table" and "semi-structured interview outline"」. The sources and methods of data collection, included: audio and video tapes, teaching files, meeting records, interview and classroom observation, classroom observation notes and informal interviews. During the study process, the researcher and teacher continually collect and analyze data and triangular correction, with a view to show a real picture of developing PBL by cooperative teachers. This study specific discovery consists of two parts, one is researcher and cooperative teacher in studies research collaboration process has developed three PBL teaching unit that is suitable for elementary school children's cognition; second, after a full year implementation, PBL teaching teachers' professional development skills have changed, for example in the next six fields:「"introduction teaching assessment and research", "discipline knowledge", "teaching knowledge and skills", "teaching design capacity", "teaching integration capacity" and "teaching environmental awareness"」.