An X-ray imaging apparatus comprising: a plurality of pixel circuits, each of the plurality of pixel circuits comprising (i) a conversion unit (302, 314, 305, 315) adapted to convert generated X-ray to an electrical signal, (ii) a sampling and holding unit (306, 308) adapted to sample and to hold the electrical signal, and (iii) a resetting unit (301, 304) adapted to reset the conversion unit (302, 314, 305, 315), wherein the conversion unit (302, 314, 305, 315) includes a photodiode unit, and an amplifier (314, 315) that amplifies electric charge generated and accumulated in the photodiode unit and converts said electric charge to the electrical signal; a selection unit (202, 203) adapted to perform a selection operation of the plurality of pixel circuits that is to output the electrical signal sampled and held by the sampling and holding unit (306,308), in order to sequentially output the electrical signal sampled and held by the sampling and holding unit (306, 308) from the plurality of pixel circuits; a control unit (101, 108) adapted to control the plurality of pixel circuits so that the reset is collectively performed to the plurality of pixel circuits, based on a synchronization signal indicative of X-ray generation timing that is detected by the control unit (101, 108), and the sampling and holding is collectively performed to the plurality of pixel circuits after a predetermined accumulation time; and a determination unit adapted to determine, when the reset is performed based on the synchronization signal, whether or not the selection operation to the plurality of pixel circuits, based on an immediately preceding synchronization signal is completed characterized in that if the determination unit determines that the selection operation of the plurality of pixel circuits is not completed during an imaging interval defined by an interval of two consecutive synchronization signals, the selection unit (202, 203) stops the selection operation of the plurality of pixel circuits in which a portion of pixel circuits, out of the plurality of pixel circuits, remains unselected, and resumes the selection operation of the plurality of pixel circuits to the portion of the pixel circuits after the control unit (101, 108) starts and finishes the reset to the plurality of pixel circuits for starting accumulation of electric charge by a plurality of photodiode unit in the plurality of pixel circuits. a plurality of pixel circuits, each of the plurality of pixel circuits comprising (i) a conversion unit (302, 314, 305, 315) adapted to convert generated X-ray to an electrical signal, (ii) a sampling and holding unit (306, 308) adapted to sample and to hold the electrical signal, and (iii) a resetting unit (301, 304) adapted to reset the conversion unit (302, 314, 305, 315), wherein the conversion unit (302, 314, 305, 315) includes a photodiode unit, and an amplifier (314, 315) that amplifies electric charge generated and accumulated in the photodiode unit and converts said electric charge to the electrical signal; a selection unit (202, 203) adapted to perform a selection operation of the plurality of pixel circuits that is to output the electrical signal sampled and held by the sampling and holding unit (306,308), in order to sequentially output the electrical signal sampled and held by the sampling and holding unit (306, 308) from the plurality of pixel circuits; a control unit (101, 108) adapted to control the plurality of pixel circuits so that the reset is collectively performed to the plurality of pixel circuits, based on a synchronization signal indicative of X-ray generation timing that is detected by the control unit (101, 108), and the sampling and holding is collectively performed to the plurality of pixel circuits after a predetermined accumulation time; and a determination unit adapted to determine, when the reset is performed based on the synchronization signal, whether or not the selection operation to the plurality of pixel circuits, based on an immediately preceding synchronization signal is completed characterized in that if the determination unit determines that the selection operation of the plurality of pixel circuits is not completed during an imaging interval defined by an interval of two consecutive synchronization signals, the selection unit (202, 203) stops the selection operation of the plurality of pixel circuits in which a portion of pixel circuits, out of the plurality of pixel circuits, remains unselected, and resumes the selection operation of the plurality of pixel circuits to the portion of the pixel circuits after the control unit (101, 108) starts and finishes the reset to the plurality of pixel circuits for starting accumulation of electric charge by a plurality of photodiode unit in the plurality of pixel circuits.