A radiation imaging apparatus includes: a detection unit configured to detect emitted radiation and output radiation image data； a clock control unit that has an internal clock and is configured to control a timing at which the detection unit is driven, based on time information of the internal clock； and a communication unit configured to transmit and receive data through a network, wherein the communication unit, if a communication traffic of the radiation image data is at a threshold or less, transmits the time information to a control apparatus that is connected through the network, and the clock control unit corrects the time information of the internal clock using time information that is a reply from the control apparatus to the time information.
