To easily connect tube and elbow.

For connecting the tube and the elbow, after covering the tip of the tube with a tube shaped coupler, the is inserted into the elbow. Next, this coupler is arranged between the recessed parts 48 and 49 of the advancing/ retreating piece 42 of the tool 31 for connecting the tube and a fixed piece 46, a motor is rotated in the normal rotation direction by operating a switch 35, and the advancing/retreating piece 42 is advanced. Consequently, the coupler is calked, and the tube and the elbow are connected. A clutch mechanism for limiting torque is provided on a motor-driven tool 33, when the coupler is sufficiently calked, the clutch is idled the, advancing/retreating piece 42 is no more advanced. When rotating the motor after changing over a changeover button 36, the advancing/retreating piece 42 is retreated. Accordingly, the fixed piece 46 is removed from a bracket 38, and the coupler is removed from the tool for connecting the tube.