本研究探究一位資深國小教師在接受論證理念前、後,於課室中實踐論證言談的改變、模式及面對的問題。參與者為教學年資19年的個案教師及其任教的一班學生。收集的資料包括60節課室觀察和6次教師訪談。質性資料分析結果發現:教師在接受論證理念前,雖然教學中已出現論證言談,但多集中在引導學生提出主張,少數為提出理由。接受論證理念後,教學中的論證言談數量增加了,類型也擴增到引導學生提出證據、反駁等較高層次的言談,但仍缺乏評鑑論點或證據的部分。而個案教師實踐論證言談出現了四種言談模式,其中「反駁模式」最能延展出較多師生或學生同儕之間的口語互動。教師實踐論證言談的問題主要來自時間的限制,且實踐初期若缺乏科學教育專業者的諮詢,教師實踐的信心和意願會受到影響。 The purpose of the study was to explore one veteran teacher’s argumentative talks through science instruction. After one-semester classroom observation, the teacher with 19-year teaching experiences received eight-week program to construct the knowledge about argumentation and argumentation instruction. Subsequently he was asked to implement argumentative talks in science class. Total 60-hour classes were observed and several individual interviews were conducted. The findings revealed that before constructing the knowledge, the teacher had showed some argumentative talks, which only focused on fostering students to make claims and few warrants. After constructing the knowledge, the teacher’s argumentative talks changed to adopt more argumentative talks to foster students to formulate rebuttals and evidence, but still lacked to encourage students to evaluate arguments or evidence. There were four modes of the teacher’s argumentative talks found. “Rebuttal mode” was the most useful mode for actively engaging students in class talks. One of the main problems to implement argumentative talks in science class was to improve students’ argumentation skills was a time-consuming process, so that it would delay the whole progress of the lessons. Meanwhile, the teacher at the beginning of implementation needed more professional assistance to enhance their self-confidence for implementing argumentation, otherwise it would influence the teacher’s willing to adopt argumentative talks in his class.