The invention provides a steel ball grinding machine, and belongs to the field of steel ball machining equipment. The steel ball grinding machine comprises a lower assembly, a millstone outer side wall, a control system and an upper assembly and further comprises an automatic unloading device. The automatic unloading device comprises a power device, a transmission device, a connecting device and an unloading door. The power device is mounted on the millstone outer side wall or the lower assembly. An actuating element of the power device is connected with the transmission device. The transmission device is mounted between the power device and a connecting part. The connecting device is mounted between the transmission device and the unloading door. The unloading door is mounted on the connecting device, and has the advantage of achieving automatic unloading of the steel ball grinding machine.