To reduce a working time by simultaneously welding upper/lower faces when welding members by friction welding.
A first panel 56 and a second panel 57 are butted, respective panel has a first plate, a second plate and a third plate connected to the first plate, the second plate is substantially parallel to the third plate, the first plate is substantially vertical to the second plate and the third plate, the first plates are butted each other, rotary tools 50, 50a are arranged at the respective sides of the second plate an the third plate of the butted part, the other rotary tool 50a is arranged in the vertical direction to one rotary tool 50, the two rotary tools are substantially are moved at the same speed, thus, friction welding is conducted.
ISHIMARU YASUO
TAKENAKA TAKESHI
