PROBLEM TO BE SOLVED: To provide a compact and simple wheel hub driving unit at low cost. SOLUTION: In this wheel hub driving unit, an axle of the wheel and a motor having an output shaft extended on the same axial center as the axle are included in a hub case fixed to a vehicle body. In the hub case, planetary gear mechanism for low speed and planetary gear mechanism for high speed outputting to the axle are stored. Sun gears in both planetary gear mechanisms are relatively rotatably provided on the output shaft. A shifter which is relatively non-rotatable and slidable in the axis center direction is provided on the output shaft. The shifter can be switched to a high speed position for transmitting power of the output shaft to the planetary gear mechanism for high speed and a low speed position for transmitting power of the output shaft to the planetary gear mechanism for low speed by sliding on the output shaft, and can be engaged/disengaged to/from at least either one of the sun gear of the planetary gear mechanism for low speed and the sun gear of the planetary gear mechanism for high speed. COPYRIGHT: (C)2010,JPO&INPIT