PURPOSE: To execute exactly a detection by inspecting a falling-out of a needle by a descending distance of an inspecting needle.

CONSTITUTION: A needle contained work 1 which has been carried on a tact base 5 by a tact pawl stops at the lower part of the same shaft of an inspecting shaft 6, and when the tact pawl returns to the original position, a cylinder 12 descends, the inspecting shaft 6 descends by its empty weight, and at the same time, a motor 9 operates and the inspecting shaft 6 repeats an oscillation at a prescribed angle. Accordingly, an inspecting needle 8 oscillates between a work 1 and a dummy shaft 2, contacts to a needle 4 and descends. In case of a non-defective unit into which a prescribed number of needles 4 are inserted, the inspecting needle 8 stops descending because a gap between the needles 4 is small, a non-defective unit dog 14 is opposed to a non-defective unit sensor 17, and it is detected to be a non-defective unit.