Method for manufacturing shaft body

A method for manufacturing a shaft body by welding a plurality of shaft members together and forming the shaft body, the method comprising:

• a primary tempering step of tempering the plurality of shaft members before welding the plurality of shaft members together;
• a welding step of welding the shaft members together after the primary tempering step to form a weld part;
• a secondary tempering step of tempering the vicinity of the weld part between the shaft members after the welding step;
• a pre-weld material forming step of forming pre-weld materials of the shaft members;
• and
• a quenching step of subjecting the pre-weld materials of the shaft members to quenching after the pre-weld material forming step and before the primary tempering step, wherein
• after the welding step, in a range continuing to a first end of one of the plurality of shaft members forming the weld part, a strength of the first end closer to the weld part is lower than the strength of a second end farther from the weld part with respect to the first end, and
• the primary tempering step is performed by changing a tempering temperature in the range and a tempering temperature outside of the range.