In a method of manufacturing a detection device including pixels on a substrate, each pixel including a switch element and a conversion element including an impurity semiconductor layer on an electrode, which is disposed above the switch element and isolated per pixel, the switch element and the electrode being connected in a contact hole formed in a protection layer and an interlayer insulating layer, which are disposed between the switch elements and the electrodes, the method includes forming insulating members over the interlayer insulating layer between the electrodes in contact with the interlayer insulating layer, forming an impurity semiconductor film covering the insulating members and the electrodes, and forming a coating layer covering an area of the protection layer where an orthographically-projected image of a portion of the electrode is positioned, the portion including a level difference within the contact hole.