本研究運用臺灣參與經濟合作暨發展組織「教學與學習國際調查」（TALIS 2018）之國中教師資料，檢驗教師專業發展、自我決定動機與工作滿意度之關聯與中介機制。選取此三個變項作為分析核心，係因TALIS 2018同時涵蓋教師專業發展經驗、教學效能與學校支持情境等可對應自我決定理論之心理需求指標，以及教師對教職與工作環境之滿意評價，能用以檢視專業發展如何透過動機內化歷程影響工作滿意度。採次級資料分析，先以描述統計呈現三變項現況，再以皮爾森相關檢視變項關聯，並運用結構方程模型同時估計直接、間接與總效果；中介效果則以Sobel檢定與Bootstrap重抽樣進一步驗證。結果顯示：三個變項整體知覺偏正向，且兩兩變項呈顯著正相關；另外，本研究採橫斷面調查數據，旨在探索變項間的結構關聯。雖模型顯示「自我決定動機」在教師專業發展與工作滿意度之間具完全中介效應，然受限於次級資料之橫斷調查性質，此結果視為變項間之關聯模式而非絕對因果定向。本研究貢獻在於：以具代表性的國際大型資料，在臺灣國中教師脈絡中實證自我決定動機之中介假設，並對教師專業發展設計提出依據。實務上，建議以目標清晰、實作導向與回饋循環之專業學習設計，結合同儕協作與支持型領導，強化自主、勝任與歸屬感之需求支持；政策上，將專業發展與教師生涯進路、職務責任與薪酬晉升連結，兼顧內外在誘因以提升參與成效；研究上，建議後續採縱貫設計與多來源測量，並視需要對接PISA等資料，以強化因果推論與測量效度。

This study used data from lower secondary teachers in Taiwan who participated in the OECD’s Teaching and Learning International Survey (TALIS) 2018 to examine the relationships among teacher professional development, self-determined motivation, and job satisfaction, focusing on the mediating role of motivation. These three variables were selected because TALIS 2018 includes indicators of teachers’ professional development experiences, teaching efficacy, and school support conditions that correspond to the psychological needs emphasized in self-determination theory, as well as teachers’ evaluations of their profession and working environment. This measurement structure allows the study to examine whether professional development is associated with job satisfaction through the process of motivational internalization. Secondary data analysis included descriptive statistics, Pearson correlations, and structural equation modeling (SEM) to estimate direct, indirect, and total effects, with mediation tested using the Sobel test and bootstrap resampling. Results showed that teachers reported generally positive perceptions across the three variables, which were significantly and positively correlated. In the SEM, professional development had no significant direct effect on job satisfaction, yet its indirect and total effects through self-determined motivation were significant, indicating full mediation. Specifically, professional development enhanced job satisfaction only when it satisfied teachers’ basic psychological needs for autonomy, competence, and relatedness, thereby fostering greater internalization and identification of motivation. Additionally, this study used cross-sectional data to explore structural relationships. While the model showed a full mediating effect, given the cross-sectional nature of secondary data, results should be interpreted as structural associations rather than definitive causal orientations. This study contributes by empirically validating the mediating role of self-determined motivation using representative international data in the context of Taiwanese lower secondary teachers and offers evidence-based implications for professional development design. Practically, professional learning should emphasize clear goals, practice-oriented activities, feedback, and supportive leadership. Policy should align teacher professional development with career pathways and promotion systems. Future research should adopt longitudinal designs and consider linking TALIS with PISA data to strengthen causal inference.