Shaft for steering device, method of manufacturing shaft for steering device, and electric power steering device

A method of manufacturing a shaft for a steering device that comprises a spline shaft part to be coupled with an input shaft, a stopper part to be coupled with an output shaft, and an intermediate shaft part that couples the spline shaft part with the stopper part, the method comprising:

• a step of forming a hole part recessed in an axial direction from one end of a pillar-shaped material by forging;
• and
• a step of pressing the material in which the hole part has been formed into a die to perform drawing in a radial direction on a portion of the material at which the spline shaft part and the intermediate shaft part are to be formed, and prolonging a length along the axial direction of the hole part at the same time by forging,
• wherein a mandrel is inserted into the hole part to perform the forging,
• the hole part includes a bottom face intersecting with the axial direction, and an inner wall surface along the axial direction,
• a metal flow at a position overlapped with the bottom face is continuously formed along the inner wall surface, and
• the metal flow in the vicinity of the inner wall surface is formed more densely than a metal flow in the vicinity of an outer circumference of the spline shaft part or the intermediate shaft part.