Motor shaft, rotor, motor and fan

A cylindrical motor shaft (9) forming a rotating shaft of a motor includes a processing target region (23), a spiral groove (10), and an anti-spiral groove (11) intersecting the spiral groove (10) atleast at one point. The processing target region (23) is provided in a range from one end (20a) on the cylindrical bottom surface (20) side to the other end (21b) on the top surface (21) side. The spiral groove (10) is provided so as to surround at least one circle of the outer peripheral surface of the processing target region (23). The anti-spiral groove (11) is provided so as to surround the outer peripheral surface of the processing target region (23) in the reverse direction of the spiral groove (10). 形成电动机的旋转轴的圆筒形的电动机轴(9)包括加工对象区域(23)、螺旋槽(10)、和至少在一处与螺旋槽(10)交叉的反螺旋槽(11)。加工对象区域(23)设置于从圆筒形的底面(20)侧的一端(20a)至顶面(21)侧的另一端(21b)的范围。螺旋槽(10)设置为围绕加工对象区域(23)的外周面至少一周。反螺旋槽(11)设置为向螺旋槽(11)的反方向围绕加工对象区域(23)的外周面。