捷運淡水線前身是廣為人知的臺鐵淡水線，於1901年8月25日通車啟用，從最初以運輸縱貫鐵路建設所需資材為目的，逐漸轉為大臺北重要的客運要道，且一路營運至1988年，並在1997年繼續以捷運的形式存在。臺鐵淡水線的沿線曾出現幾條側線，雖知名度較低，但卻是這條路線演進過程的一部份。因此，本文透過臺鐵的相關公文及檔案，以及比對各類古地圖與航照圖，將臺鐵淡水線曾出現之5條側線進行討論與探究，補足過去研究缺漏的一塊拼圖。

The predecessor of the MRT Tamsui Line was the well-known Taiwan Railway Tamsui Line, which commenced service on August 25, 1901. It was built for transporting building materials of the Western Trunk Line construction, and evolved into a significant passenger transportation route in Taipei area. It remained in operation until 1988 and was transformed into a MRT Line in 1997. There were several branch lines contributing to the evolution of the Taiwan Railway Tamsui Line, even with less public attention. This article examines five branch lines based on documents and records from the Taiwan Railway, historical maps, and aerial photographs. The objective of this research is to fill a vacancy of the previous studies.