A gearbox includes a sun gear, a plurality of planetary gears meshed with the sun gear, a rotating frame supporting the planetary gears, and a housing with an internal ring gear meshed with the planetary gears. The planetary gears include a first gear and a second gear coaxially connected to each other along an axial direction and rotating synchronously, the first gear meshed with the sun gear, and the second gear meshed with the internal ring gear of the housing. The rotating frame received in the housing has an upper frame and a lower frame with a central hole, each of the plurality of planetary gears is arranged between the upper frame and the lower frame by a mounting pin, the lower frame is supported by a flange connected to the housing, the sun gear is driven to rotate so as to operate the rotating frame. The gearbox of the present disclosure has low vibration and low noise.