An X-ray image processing apparatus according to an embodiment includes a specifying unit and a decision unit. The specifying unit processes a first X-ray image based on an output signal from an X-ray detector influenced by the action of an electromagnetic field, and specifies noise characteristics unique to noise components which are contained in the first X-ray image and originate from the action of the electromagnetic field on the X-ray detector. The decision unit decides filter characteristics for reducing the noise components which are contained in the first X-ray image and originate from the action of the electromagnetic field on the X-ray detector based on the specified noise characteristics.