To provide an article detector which can detect completely and article passing through or positioned in a detecting area even if an obstacle exits.

Light emitting diodes 1 and light-receiving diodes 2 are disposed so as to face each other, and the light-receiving diode 2 which cannot receive the irradiated light from the light emitting diode 1 due to obstacles 24C, 24D existing in an detecting area A formed between the light emitting diode 1 and the light receiving diode 2 is stored by a non-operation storage part 9. Whether an article M stored in a storage bucket from an article storage tray passes through or exists is detected using the light emitting diode 1 and the light receiving diode 2, excluding the light-receiving diode 2 stored in the non- operation storage part 9.