A radiation imaging apparatus comprises: an imaging means (20) for capturing a moving image of an object irradiated with radiation a first extraction means (106,202) for extracting an object area where an object exists from an exposure field region of radiation in a first frame image of the moving image a second extraction means (106,203) for extracting a region of interest as a target for calculation of a first feature amount indicating a feature of an image from a region corresponding to the object area in a second frame image following the first frame image a first calculation means (106,204) for calculating the first feature amount of a region of interest in a third frame image following the second frame image from a region corresponding to the region of interest in the third frame image and a control means (109) for controlling a radiation generating means (109) based on the first feature amount.
