The invention discloses an incomplete steel ball automatic sorting device of a steel ball conveyor, and belongs to steel ball forming machinery. The steel ball conveyor comprises a frame, a rolled steel ball feeding mechanism and a power transmission mechanism, wherein the frame is provided with a steel ball inlet groove and a steel ball outlet groove; the rolled steel ball feeding mechanism is installed on the frame; the power transmission mechanism is arranged on the frame; the incomplete steel ball automatic sorting device comprises a first steel ball rejecting roll, a second steel ball rejecting roll, a first transmission gear, a second transmission gear, a steel ball rejecting roll transmission mechanism and a center roll; a first screwed flange and a second screwed flange are formed on the first steel ball rejecting roll and the second steel ball rejecting roll; the first transmission gear and the second transmission gear are mutually meshed; the steel ball rejecting roll transmission mechanism is arranged on the frame; the center roll is positioned between the first steel ball rejecting roll and the second steel ball rejecting roll; the distance from the center roll to the first steel ball rejecting roll is equal to that from the center roll to the second steel ball rejecting roll, and is smaller than the diameter of a complete steel ball; and first and second incomplete steel ball outlet cavities are formed at bottoms of steel ball inlet and outlet grooves. The device embodies the effect of automatically rejecting unqualified steel balls, guarantees the safety, guarantees the normal operation of a subsequent quenching machine, and saves human resource.