PURPOSE: To form a flare part and a flange part to the leading end of a resin tube by simple molding processing.

CONSTITUTION: A mold is constituted by providing a through-hole 22 to the center position of split mold main body parts so as to pierce the mold up and down and a mold inserting recessed part is provided to the upper surface of the mold. A first circular recessed part is provided to the surface of the mold inserting recessed part. A movable mold has a tube inserting hole 31 at the center thereof and a funnel-shaped part 32 is coaxially provided to the tube inserting hole from the upper surface of the hole toward the interior thereof and a second recessed part is provided to the bottom surface thereof. A gap is provided between the movable mold and the mold inserting recessed part by a coil spring 26a. A resin tube 10a is inserted in the tube inserting hole and a pressure terminal is inserted in the tube and ultrasonic waves are applied to the tube while the pressure terminal is pushed to heat the tube to obtain an outer casing 10 having a funnel-shaped flare part at the end part thereof and having a ring-shaped flange part 12 inside the flare part 11.