An X-ray imaging apparatus suppresses X-ray irradiation outside an X-ray detection unit. An X-ray imaging apparatus according to this invention includes an X-ray irradiation unit which irradiates an object with X-rays, an X-ray detection unit movably provided with an imaging unit, a first irradiation field prediction unit which calculates an irradiation field by using the relative positional relationship between generation unit and imaging unit and aperture value of a collimator, a second irradiation field prediction unit which calculates an irradiation field based on the dose of X-rays generated by the generation unit and the X-ray dose distribution detected by the imaging unit, and a predicted irradiation field decision unit which decides, as a predicted irradiation field, a region including one or both of irradiation fields respectively calculated by the first and second irradiation field prediction units.