Provided is a security item using the intensity of fluorescent materials and a user identification system using same, the security item containing fluorescent materials that have intrinsic luminescent characteristics when irradiated with excitation light, wherein the fluorescent materials are contained in an amount of 0.2-3.0 wt % on the basis of the weight of the security item, and the difference in relative value calculated by formula (I), according to a 0.2-0.5 wt % difference in the amount of the fluorescent materials, is at least 3. Formula (I): the relative value of χ wt % of fluorescent materials=(the relative intensity of the emission wavelength of χ wt % of the fluorescent materials×100)/(the relative intensity of the emission wavelength of 3.0 wt % of the fluorescent materials).