An X-ray imaging apparatus includes an FPD and short-circuited pixels. The FPD has pixels arranged in arrays for detecting an X-ray image. The short-circuited pixels detect a radiation dose of X-rays in the FPD. The X-ray imaging apparatus is changed over between first and second operating modes. The first operating mode is selected in case of combining with an X-ray generating apparatus with communication compatibility, and performs an exposure control for controlling a total radiation dose according to a detection signal from the short-circuited pixels. The second operating mode is selected in case of combining with an X-ray generating apparatus with communication incompatibility, and performs control of start synchronization for synchronizing operation of the FPD with the emission start of X-rays according to a detection signal from the short-circuited pixels. Thus, control of the X-ray imaging apparatus is changed over appropriately.