A photodiode array is provided and includes insulating substrate; photodiodes arrayed in detection region of insulating substrate, photodiodes configured to output signal in accordance with light incident on photodiodes; first switching elements corresponding to photodiodes and including first semiconductor made of oxide semiconductor; gate lines coupled with first switching elements and extending in first direction; signal lines coupled with first switching elements and extending in second direction intersecting first direction; and gate line drive circuit including second switching element that includes second semiconductor made of polycrystalline silicone, gate line drive circuit being provided in peripheral region outside detection region and configured to drive gate lines, wherein photodiodes includes translucent conductive layer that is cathode, and translucent conductive layer overlaps none of signal lines in plan view.