A radiation imaging apparatus comprises a conversion element and a transistor. A drive unit performs a reset operation at a plurality of times, by supplying a conducting voltage to gates of the transistors, successively, one row by one row, an operation of stopping the supplying of the conducting voltage responsive to detecting the irradiation of the radiation to perform an accumulation operation and, after the reset operation, a read out operation. During the reset operation, a period between the supplying the conducting voltage to the gates of the transistors in one row and the supplying the conducting voltage subsequently to the gates of the transistors in another row is different from a period between the supplying the conducting voltage to the gates of the transistors in the another row and the supplying the conducting voltage subsequently to the gates of the transistors in further another row.