In a method of manufacturing a detection device including a plurality of pixels arrayed on a substrate, the pixels each including a switch element and a conversion element including an impurity semiconductor layer disposed on an electrode, which is disposed above the switch element, which is isolated per pixel, and which is made of a transparent conductive oxide joined to the switch element, and further including an interlayer insulating layer, which is made of an organic material, which is disposed between the switch elements and the electrodes, and which covers the switch elements, the method includes insulating members each made of an inorganic material and disposed to cover the interlayer insulating layer between adjacent two of the electrodes in contact with the interlayer insulating layer, and forming an impurity semiconductor film covering the insulating members and the electrodes and becoming the impurity semiconductor layer.