An X-ray detector provided for a radiation image pickup apparatus of this invention includes two types of areas, i.e. an image area for X-ray detection, and an image area for time variation noise detection to detect time variation noises generating from circuits of the X-ray detector. Consequently, time variation noises can be detected properly, regardless of damage to gate circuits of an active matrix substrate, by reading charge signals from the image area for time variation noise detection before a gate drive circuit is set to ON. As a result, a radiation image pickup apparatus with improved image quality can be manufactured.
