The invention discloses a feeding device of a feed mixer. The feeding device comprises a feeding device body; a feed hopper is arranged on the upper part the feeding device body; a filter screen of the feeding device body is arranged below the feed hopper; a discharge port is arranged the right bottom of the filter screen; a solenoid valve of the feeding device body is arranged below the filter screen; an electromagnetic heating coil of the feeding device body is arranged below and outside the solenoid valve; a rotating shaft is arranged in the electromagnetic heating coil; an impeller is arranged above the rotating shaft; a drive motor is arranged at the right lower side of the feeding device body; and a feed outlet is fixedly arranged at the left lower side of the feeding device body, the feeding device is fixed below the left body control device. The feeding device of the feed mixer has the advantages of reasonable structural design, simple operation and good mixing effect, can be used for stirring feed and controlling the discharging speed. Therefore, the feeding device of a feed mixer can be widely promoted and applied.