To facilitate loading/unloading operation by forming one or both of loading/unloading couple parts out of a shape memory member in a coupler for connecting a medical tube used for the connection of a container holding a dialysis liquid and a nutriant and the like to a catheter or the like.

In a peritoneal dialysis therapy, a transfer tube 6 is connected to a peritoneal catheter which is inplanted into an abdominal cavity of a patient by surgeric operation and the tube 6 is linked to a bag tube 8 connected to a dialysis liquid bag made of a soft resin holding a dialysis liquid to inject the dialysis liquid into the abdominal cavity. To connect both the tubes 6 and 8, a coupler 7 which comprises a male part 10 and a female part 11 is used and the female part 11 is made of a shape memory alloy. The female part 11 is softened below 20°C to be made free to deform by an external pressure and returned to a shape stored above 20°C. Thus, a coupling is possible by tightening the male part 10 elastically like rubber.