An X-ray holography light source element divides an entering X-ray beam to emit two or more mutually coherent X-ray beams. The light source element includes an X-ray waveguide which has a core and a cladding. The core contains a plurality of substances different in a refractive-index real part and is a periodic structure body in which basic structures are periodically disposed; the cladding confines an X-ray to the core to be guided therethrough. The total reflection critical angle of the X-ray on the interface of the core and the cladding is larger than the Bragg angle corresponding to the periodicity of the basic structures of the core. A shield member provided with two or more opening portions for respectively emitting the two or more mutually coherent X-ray beams is disposed at the end portion at an emission side of the X-ray waveguide.