The invention relates to a drilling tool, in particular to an adjustable-length drilling tool. The adjustable-length drilling tool comprises a tool handle, a tool body and a tool head. The tool body comprises a first tool body portion provided with the tool head, and a second tool body portion arranged between the first tool body portion and the tool handle. The first tool body portion and the second tool body portion are provided with spiral chutes correspondingly. A connecting shaft is formed by extending from the middle of the end, connected with the first tool body portion, of the second tool body portion along the central axis. An axial hole corresponding to the connecting shaft is arranged at the end, connected with the second tool body portion, of the first tool body portion. The connecting shaft is in interference fit with the axial hole. According to the adjustable-length drilling tool, the number of the second tool body portion can be adjusted according to the practical drilling depth, and when a certain section of the tool body portions is damaged, the section of tool body portion can be replaced for continuous application, so that the adaptability is high.