According to an embodiment, a detecting element includes a first electrode, a second electrode, an organic conversion layer, a third electrode. The first electrode and the third electrode are configured to keep different potentials by DC power supply. The organic conversion layer is disposed in between the first electrode and the second electrode, and is configured to convert energy of radiation into electrical charge. The third electrode is disposed at least either in the organic conversion layer, or in between the organic conversion layer and the first electrode, or in between the organic conversion layer and the second electrode, and is at least partially covered by an insulating film.