本研究在探討臺灣北部地區國小中年級學童分數概念的等分、簡單分數、分數單位量、分數等量及等值分數等子概念的表現。研究方法採筆測及一對一半結構式面談進行。 研究結果顯示學童運用整數知識來處理分數問題並將分數的分子、分母視為獨立的二個數，普遍存在在各試題的表現上；學童解判斷是否等分問題時，只注意到被分割的塊數，而忽略分割後的每一塊是否相等；學童對於單位量、內容物的單位詞出現混淆的情形；中年級學童較習慣用全部內容物當單位量；學童在面對餘量再分問題時會自行增加或減少內容物，使其數量可以整數個分配；許多學童在比較分數大小時，直接將分子和分母分開來進行比較，而不足將分數視為一個量來比較。同時研究也顯示中年級學童一半和二分之一的連結並不穩固。 根據研究結果，本研究對國小分數教材和教學、評量及未來研究方向提出一些建議。

　　　　　The study aims to investigate middle-grader's understanding of sub-concepts in fraction, including equal-sharing, simple fraction, unit, equal-quantity and equivalence fraction in northern Taiwan. The research methods are paper-and-pencil test and one-to-one semi-structural interviews. The result shows that the students applied their knowledge of integer to deal with the problems of fraction and they regarded numerator and denominator as separate numbers. This phenomenon was evident in students' problem solving strategies. When judging the problems of equal-sharing, they only noticed the number of parts but neglected to judge if each part was equal. Students were confused by the unit terms of unit and content. Middle-graders tended to take the whole content as unit. When the remainder needed to be divided, students added or deducted the content to make the content divisible by integer. Many students compared numerator and denominator separately instead of comparing them as an amount when comparing fractions. Besides, the research also found that the connection between half and one half was not held very solidly by middle-graders. This research will bring up some suggestions for the material, teaching, evaluation and future research on fraction teaching in elementary school.