[Issue] To provide a connecting structure for a gastrostomy catheter and a fluid supply tube with which the gastrostomy catheter is not pressed into the body when a fluid supply tube is connected thereto and with which the gastrostomy catheter is not removed from the patients body even if the fluid supply tube is pulled. [Means of Resolution] A part to be engaged 11c is formed on an external holding part 11 of a gastrostomy catheter 10, and an engaging part 22 is provided at the tip end of a fluid supply tube 20, and a connecting member 30 comprises a guide part 32 and an engaging part 31, both of which are substantially C-shaped, and a linking part 33 which links the guide part 32 and the engaging part 31. The connecting member 30 is assembled with the external holding part 11, and the fluid supply tube 20 can be placed in communication with the external holding part 11 by pushing the engaging part 22 sideways between the external holding part 11 and the guide part 32, and the engagement between the engaging part 31 and the part to be engaged 11c can be released by pulling the fluid supply tube 20.
