the optical information recording / reproduction device for recording information by irradiating an optical information recording medium with signal light and reference light to form a hologram , and reproducing the information by irradiating the hologram with the reference light , wherein the optical information recording / reproduction device is provided with a branching element for branching laser light from a laser light source into signal light and reference light , a spatial light modulation unit for adding two - dimensional information to the signal light , an objective lens for irradiating an optical information recording medium with the signal light , a photodetector for detecting diffracted light from the optical information recording medium when irradiated with the reference light , and an optical axis adjustment unit disposed between the laser light source and the branching element , the optical axis adjustment unit adjusting the optical axis of the laser light .