1. An X-ray image processing apparatus comprising: a setting unit adapted to set a parameter for processing an X-ray image acquired by an X-ray receiving unit in order to decrease a noise of the X-ray image on the basis of a difference value of a first dark image and a second dark image, wherein the first dark image is acquired when no X-rays are irradiated and before the X-ray image is acquired, and the second dark image is acquired when no X-rays are irradiated and after the X-ray image is acquired; and an image processing unit adapted to perform image processing on the X-ray image on the basis of the parameter set by said setting unit.