Provided is a fluorescent labeling material, including zinc oxide nanoparticles each surface-modified with an organic compound having an amino group placed at an outer end thereof. Also provided is a fluorescent labeling agent to be used in vivo or in vitro, including the fluorescent labeling material, in which: EDC or the like is bound thereto through the amino group; and a substance capable of selectively binding to a target to be fluorescently labeled, such as an antibody, is linked thereto.