A multilayer target 5 is composed of a first layer 5a, a second layer 5b and a third layer 5c which are made of different materials. When an electron beam 13 is incident upon the multilayer target 5, the electron beam 13 arrives at the third layer 5c, and X-rays Xa, Xb and Xc, the radiation qualities of which are respectively suitable for the characteristics of the first layer 5a, the second layer 5b and the third layer 5c, are generated.