An information recording/reproducing device includes a radiation light source 1 such as a semiconductor laser, a spatial modulation element 6 that splits laser light 2 emitted from the radiation light source 1 into a large number of diffracted light rays, and an objective lens 7 that converges the large number of diffracted light rays onto different points. The laser light 2 emitted from the radiation light source 1 is split into a large number of diffracted light rays by the spatial modulation element 6, the large number of diffracted light rays are converged onto different points in the photosensitive layer 8b of the information recording medium 8 by the objective lens 7, and information is recorded in the photosensitive layer 8b of the information recording medium 8, using an assembly of these converging points. Accordingly, it is possible to provide an information recording device capable of realizing high-contrast recording in which stray light or diffraction has no influence during signal recording.