The invention provides a technique inhibiting entry of moisture to an active matrix substrate included in an X-ray imaging device.An active matrix substrate includes, in each of the pixels, a photoelectric conversion element including a pair of electrodes and a semiconductor layer provided between the pair of electrodes, a first flattening film configured as an organic resin film and covering the photoelectric conversion element, and a first inorganic insulating film covering the first flattening film. The first flattening film and the first inorganic insulating film are provided to extend outside the pixel region. Outside the pixel region, the first flattening film is covered with the first inorganic insulating film to prevent exposure of the first flattening film.