A radiation imaging apparatus comprising: a pixel unit in which a plurality of pixels each including a conversion element configured to convert radiation into charges, and a switch element are arranged in a matrix; a driving circuit configured to control the switch elements via a plurality of drive lines (Vg) extending in a row direction; a bias power supply unit configured to supply a bias potential to the conversion element via a bias line (Bs); a plurality of column signal lines (Sig) to which signals are output from the plurality of pixels via the switch elements; and a detection unit, wherein the plurality of pixels include a first pixel and a second pixel, which are adjacent to each other in the row direction and are connected to a common column signal line in the plurality of column signal lines (Sig), the switch element of the first pixel and the switch element of the second pixel are connected to drive lines different from each other in the plurality of drive lines (Vg), and the detection unit determines presence/absence of radiation irradiation based on a current flowing to the bias line (Bs), the bias power supply unit includes a first bias power supply unit and a second bias power supply unit, the bias line includes a first bias line connected to the first bias power supply unit, and a second bias line connected to the second bias power supply unit and electrically independent of the first bias line, the conversion element of the first pixel is connected to the first bias power supply unit via the first bias line, and the conversion element of the second pixel is connected to the second bias power supply unit via the second bias line, characterized in that the detection unit acquires a first signal value representing a current flowing to the first bias line when the switch element of a pixel in pixels whose conversion elements are connected to the first bias power supply unit in the plurality of pixels is in a conduction state, and a second signal value representing a current flowing to the second bias line when the switch element of a pixel whose conversion element is connected to the second bias power supply unit in the plurality of pixels is in a non-conduction state such that sampling timings at least partially overlap, and determines the presence/absence of radiation irradiation based on the first signal value and the second signal value. the plurality of pixels include a first pixel and a second pixel, which are adjacent to each other in the row direction and are connected to a common column signal line in the plurality of column signal lines (Sig), the switch element of the first pixel and the switch element of the second pixel are connected to drive lines different from each other in the plurality of drive lines (Vg), and the detection unit determines presence/absence of radiation irradiation based on a current flowing to the bias line (Bs), the bias power supply unit includes a first bias power supply unit and a second bias power supply unit, the bias line includes a first bias line connected to the first bias power supply unit, and a second bias line connected to the second bias power supply unit and electrically independent of the first bias line, the conversion element of the first pixel is connected to the first bias power supply unit via the first bias line, and the conversion element of the second pixel is connected to the second bias power supply unit via the second bias line, characterized in that the detection unit acquires a first signal value representing a current flowing to the first bias line when the switch element of a pixel in pixels whose conversion elements are connected to the first bias power supply unit in the plurality of pixels is in a conduction state, and a second signal value representing a current flowing to the second bias line when the switch element of a pixel whose conversion element is connected to the second bias power supply unit in the plurality of pixels is in a non-conduction state such that sampling timings at least partially overlap, and determines the presence/absence of radiation irradiation based on the first signal value and the second signal value.