Provided is a radiation detecting element that has high adhesion between electrode portions and a substrate and does not suffer from performance failures due to insufficient insulation between the electrode portions, even if a distance between the electrode portions is narrower in order to obtain a high-definition radiation drawn image. The radiation detecting element includes: a plurality of electrode portions; and an insulating portion provided between the electrode portions on a surface of a substrate made of a compound semiconductor crystal containing cadmium telluride or cadmium zinc telluride, wherein an intermediate layer containing tellurium oxide is present between each of the electrode portions and the substrate, and wherein tellurium oxide is present on an upper portion of the insulating portion, and the tellurium oxide on the upper portion of the insulating portion has a maximum thickness of 30 nm or less.