To provide a gastrostomy tube extension device which can facilitate the insertion or removal operation in and from the patient, as well as to increase the simplicity of manufacture without sacrificing safety of operation. [Solving Means] A gastrostomy tube extension device 20 used for inserting or taking out the gastrostomy tube 10 into/from the hole on the patient includes a rod 21, a fixing member 22, and an engaging member 23. The rod 21 is formed of a rod-shaped member, and is formed with engaging stepped portions 24a on the proximal portion thereof. The fixing member 22 is adapted to be capable of moving along the longitudinal direction of the rod 21, and an engaging projection 35 which can be fixed to the tube member 11 is formed on the peripheral surface of the fixing member 22. The engaging member 23 includes a lower engaging portion 26 engageable with the engaging projection 35 and an upper engaging portion 27 which is engageable with the engaging stepped portion 24a. This assembly allows the extension to be locked, allowing the operator to manipulate the device with a single hand.
