In an apparatus without a helical movement, a reconstruction error considerably increases as a radiation angle increases. In a prior art embodiment, for example, a one-side value of the radiation angle is 9.5 degrees, and it is predicted that the reconstruction error at its periphery considerably increases. In a radiation imaging apparatus including a radiation generating source for radiating radiation to a subject, a rotating unit for rotating the subject exposed to the radiation from the radiation generating source, and a two-dimensional detector for detecting radiation, a distance between the radiation generating source and the two-dimensional detector is approximately set to a value equal to or more than 240 cm.