Propeller shaft manufacturing method and propeller shaft

A method of manufacturing a propeller shaft transmitting a driving force of a vehicle comprising:

• a first step of forming, by plastic working of metal material, a first tubular member having a first tubular portion and a first joint portion seamlessly integrated with the first tubular portion at a first end portion in a direction of a rotation axis of the first tubular portion;
• a second step of forming, by plastic working of metal material, a second tubular member having a second tubular portion and a second joint portion seamlessly integrated with the second tubular portion at a first end portion in a direction of a rotation axis of the second tubular portion;
• and
• a third step of welding a first opening end portion formed at a second end portion located on an opposite side to the first end portion of the first tubular portion so as to be thinner than a thickness of the first end portion of the first tubular portion and a second opening end portion formed at a second end portion located on an opposite side to the first end portion of the second tubular portion so as to be thinner than a thickness of the first end portion of the second tubular portion, and of forming a welding portion whose thickness is thinner than the thickness of the first end portion of the first tubular portion and also thinner than the thickness of the first end portion of the second tubular portion.