A mobile device includes a body, a motor, a transmission assembly and two driven components. The motor and the transmission assembly are disposed at the body. The transmission assembly includes a differential, two shafts and two stoppers. The differential is coupled to the motor. The two shafts are respectively coupled to the two opposite sides of the differential. The two stoppers are respectively disposed corresponding to the two shafts. The two driven components are respectively connected to the two shafts. When one of the two shafts is locked by the corresponding stopper, the motor may still drive the other shaft and the driven component connected thereto to rotate relative to the body through the differential. A transmission assembly is also provided.
