This radiation detector is provided with: a plurality of control lines extending in a first direction; a plurality of data lines extending in a second direction which intersects the first direction; photoelectric conversion units which are electrically connected to the corresponding control line and the corresponding data line, and each of which includes a photoelectric conversion element; scintillators provided on the plurality of photoelectric conversion units; a bias line which is electrically connected to the plurality of photoelectric conversion elements; a voltage generating circuit which is electrically connected to the bias line; and a radiation incidence determining circuit which is electrically connected to the bias line, and which detects a voltage change that occurs when incidence of radiation begins.
