[Issue] To provide a connecting structure for a gastrostomy catheter and a fluid supply tube with which the gastrostomy catheter does not press the body, the flow of fluid is smooth, and leakage is unlikely to occur.[Means of Resolution] A fitting groove is formed on the outer peripheral surface of an external holding part. A connecting member comprises a fitting part, a guide part, and a linking part main body which links the fitting part and guide part, and the fitting part is fitted into the fitting groove with the guide part positioned above an upper opening of the external holding part. Furthermore, a cylindrical engaging part is provided towards the tip end of the tube main body, and the engaging part can engage between the external holding part and guide part in a state in which the tip end of the tube main body is in communication with the upper opening of the external holding part by pushing the engaging part between the external holding part and the guide part so as to introduce the tube main body into the guide part from the open side thereof.
