本質化敘事研究旨在探討英語教師如何於正規及非正規專業發展領域中發展個人職能概念。研究對象為一位擁有多年補教與國高中教學經驗的英語教師。研究方法主要包含研究對象的口說敘述及半結構式訪談，目的在於完整記載研究對象之動態專業發展歷程。資料分析方式採用¬「整體─內容」分析法 (Lieblich, Tuveal-Mashiasch, & Zilber, 1998)與「關鍵事件」方法 (Webster & Mertova, 2007)。研究結果顯示，研究對象之教師發展出自於其主動作為並連結至其認為之與教學相關之要務。其中引領研究對象教師發展之關鍵為其個人與其所在之補教或學校場域的互動關係。也就是說，她如何看待及解讀場域中有關於教學與教師之價值，並以此價值為基礎發展個人職能概念。此外，研究對象之教師職能概念為一螺旋型過程，其過程強調一學習過程之結束引領另一新的學習發展；於專業發展領域之互動中動態發展。另一方面，藉由研究對象於正規與非正規學校場域中發展職能概念之經驗對照，本質化個案研究對於宏觀之正規及非正規教育系統在協助教師發展的設計，目前所面臨的兩難獲得更深入的了解。本研究期許針對教師教育、甚至於教育政策持續改善，提供可能之方向，使其更能符合教師於個人職能發展的實際需要。在本研究最後，針對於研究結果提出教學與研究上之建議做為參考。 / This study explores the development of an English teacher’s professional identity across formal and informal educational contexts. The informant invited in the study is an English teacher who has cross-contextual professional development experience. Data collection methods primarily included an oral narrative and semi-structured interviews in order to document the dynamic professional development trajectory of the teacher informant. The data collected were analyzed with a holistic-content method (Lieblich, Tuveal-Mashiasch, & Zilber, 1998) and a critical events approach (Webster & Mertova, 2007). The findings of the study indicate that teacher development is undertaken by the teacher herself and her concerns. What is really critical in guiding teacher development is the interaction between the teacher and her contexts; namely, how the teacher perceives and interprets the value of teaching and the meaning of being a teacher from the contexts, which is the basis to develop her professional identities. Furthermore, teacher professional identity is constructed dynamically as a spiral process in interaction with contexts. A better understanding of the tensions existing in the macro-level formal educational system is also obtained in the comparison with formal and informal professional development experience of the English teacher in the study. The study provides a possible direction for further improvement of teacher education program and for educational policy reforms to better take care of the actual professional development needs of teachers. Based on the findings, pedagogical implications as well as suggestions for future research are also provided at the end of the thesis.