A heel effect compensation filter is configured to have a thickness
distribution that uniforms an X-ray intensity angular distribution that
is nonuniform in the body axis direction of a subject in an X-ray flux
irradiated space. The space is formed by an X-ray flux diverging from an
anode in a body width direction of the subject and diverging in a shape
of an approximate sector in the body axis direction due to the heel
effect, when the X-ray flux generated on the anode by irradiating a
thermoelectron beam flux from a cathode to the anode is irradiated on the
subject. The thickness distribution can be obtained using a predetermined
formula.