The invention discloses a powder mixing device. The device comprises a base, a stirring assembly, a returning assembly and a mixing barrel which is arranged on the base, wherein a vibrating cylinder is arranged between the base and the mixing barrel; the stirring assembly comprises a first motor, an inner rotating shaft with stirring blades and an outer rotating shaft with stirring blades, and thetop and the bottom of the inner rotating shaft are exposed outside the outer rotating shaft, a first driven bevel gear is arranged at the top end of the inner rotating shaft, and a second driven bevel gear is arranged at the top end of the outer rotating shaft, a driving gear is arranged on an output shaft of a first motor, the first driven bevel gear is meshed with the upper end of the driving gear, and the second driven bevel gear is meshed with the lower end of the driving gear; the returning assembly comprises a second motor and a returning screw conveyer connected with an output shaft ofthe second motor, the returning screw conveyer is sleeved with a returning pipe, a returning material inlet is formed in the bottom of the returning pipe, a returning material outlet and a side walldischarging pipe penetrating the mixing barrel are arranged at the top of the returning pipe, and an electromagnetic valve switch is arranged at the returning material outlet.