The purpose of this study was to analyze the process of a teacher evaluation, its difficulties, and its impacts in an elementary school. To achieve the above purpose, this study adopted the qualitative approach to collect data by observing, interviewing, and analyzing documents. The subject of the study was a large-sized elementary school in Taipei, which participated in the 'formative teacher evaluation project' supported by Ministry of Education. The results of the study are presented as follows: 1. Four phases were formed during the process of the teacher evaluation: (1) Preparation, (2) Initiation of the professional development program, (3) Implementation, and (4) Modification. 2. The consequences of implementing teacher evaluation were that it could help promote profession growth, teaching effectiveness, and the teachers' action research. 3. Four main difficulties were confronted in implementing the teacher evaluation: (1) Teachers are not aware of the evaluation plan, (2) Teachers are divided into two groups-participants and non-participants, (3) Teachers' competency on the evaluation isn't adequate, and (4) Teachers don't have enough time to prepare and conduct the evaluation. Based on the above results, the present study also made several suggestions.