A multi-color X-ray generator includes an electron beam generator 10 which accelerates an electron beam to generate a pulse electron beam 1 and which transmits the beam along a predetermined rectilinear orbit 2, a composite laser generator 20 which successively generates a plurality of pulse laser lights 3a, 3b having different wavelengths, and a laser light introduction device 30 which introduces the pulse laser lights along the rectilinear orbit 2 to be opposed to the pulse electron beam 1, so that the plurality of pulse laser lights 3a, 3b successively head-on collide with the pulse electron beam 1 along the rectilinear orbit 2 so as to generate two or more types of monochromatic hard X-rays 4 (4a, 4b).