To easily obtain an image of burr generated at the boundary edge between holes continuously formed from the outer face into the inner portion of a molding.

To obtain an image of burr generated at the boundary edge between the holes continuously formed from the outer surface into the inner portion of the molding, an illuminating device 1 for detecting burr, emitting a light to the boundary edge and the nearby area, includes: a luminaire 2 having a luminescent material (an LED chip 5) and a cover part 6, having a light diffusion part 7, covering the luminescent material, capable of illuminating whole of the boundary edge and the nearby area; a rod having the luminaire 2 at the tip to insert the luminaire 2 into the hole; and a driving power source 16 of the luminaire 2.