An electric machine comprising: a shaft assembly comprising a first shaft, a second shaft coaxially disposed within an inner circumference of the first shaft, and a bearing disposed between the first shaft and the second shaft; a first revolving body coaxially connected to the first shaft, wherein the first revolving body comprises an annular first adapter bracket, and a tubular structural portion extending in an axial direction is disposed at an inner circumference of the first adapter bracket; a second revolving body coaxially connected to the second shaft and disposed around and at an outer circumference of the first revolving body; and a guiding assembly disposed between the tubular structural portion and the first shaft to restrict a movement of the first revolving body relative to the first shaft in a circumferential direction and a radial direction, characterized in that, the guiding assembly comprises a first inserting portion and a first socketing portion that are engaged with each other, the first inserting portion is disposed at an inner circumference of the tubular structural portion and extends in the axial direction, and the first socketing portion is disposed at an outer circumference of the first shaft and extends in the axial direction, the first inserting portion comprises a first guiding rib protruding in the radial direction from the inner circumference of the tubular structural portion, the first socketing portion is a first guiding groove recessed in the radial direction from the outer circumference of the first shaft, and the first guiding groove has a width along the circumferential direction matched with a width of the first guiding rib along the circumferential direction, and the first inserting portion further comprises a second guiding rib protruding in the radial direction from the inner circumference of the tubular structural portion, the second guiding rib has an inner diameter larger than an inner diameter of the first guiding rib, the second guiding rib and the first guiding rib are alternately arranged in the circumferential direction on the inner circumference, and the outer circumference of the first shaft has an outer diameter matched with the inner diameter of the second guiding rib. a shaft assembly comprising a first shaft, a second shaft coaxially disposed within an inner circumference of the first shaft, and a bearing disposed between the first shaft and the second shaft; a first revolving body coaxially connected to the first shaft, wherein the first revolving body comprises an annular first adapter bracket, and a tubular structural portion extending in an axial direction is disposed at an inner circumference of the first adapter bracket; a second revolving body coaxially connected to the second shaft and disposed around and at an outer circumference of the first revolving body; and a guiding assembly disposed between the tubular structural portion and the first shaft to restrict a movement of the first revolving body relative to the first shaft in a circumferential direction and a radial direction, characterized in that, the guiding assembly comprises a first inserting portion and a first socketing portion that are engaged with each other, the first inserting portion is disposed at an inner circumference of the tubular structural portion and extends in the axial direction, and the first socketing portion is disposed at an outer circumference of the first shaft and extends in the axial direction, the first inserting portion comprises a first guiding rib protruding in the radial direction from the inner circumference of the tubular structural portion, the first socketing portion is a first guiding groove recessed in the radial direction from the outer circumference of the first shaft, and the first guiding groove has a width along the circumferential direction matched with a width of the first guiding rib along the circumferential direction, and the first inserting portion further comprises a second guiding rib protruding in the radial direction from the inner circumference of the tubular structural portion, the second guiding rib has an inner diameter larger than an inner diameter of the first guiding rib, the second guiding rib and the first guiding rib are alternately arranged in the circumferential direction on the inner circumference, and the outer circumference of the first shaft has an outer diameter matched with the inner diameter of the second guiding rib.