The passive gamma spectroscopy (PGS) is a useful technique to extract information on spent nuclear fuels without any destructive actions. This method requires a correlation between number densities (NDs) of target nuclides, and it is generally estimated by numerical simulation. Therefore, prediction accuracy of these nuclides generations is one of key issues in PGS. Nuclear data used in nuclear fuel depletion calculations is one of dominant uncertainty sources, so we quantify nuclear data-induced uncertainties of NDs of six fission product nuclides, which are important in PGS: Ce-144, Cs-134, -137, Ru-106, Sb-125 and Eu-154. Generation mechanisms of these nuclides are quantitatively investigated through sensitivities of these NDs to nuclear data, which can be calculated by the depletion perturbation theory. With the sensitivities and covariance data of nuclear data, uncertainties of NDs of these nuclides are quantified with the JENDL libraries and others. The uncertainties of Ce-144, Cs-137 and Ru-106 are less than 2%, and that of Sb-125 is around 6%. In these uncertainties, fission yields uncertainties are dominant. On the Cs-134 and Eu-154 generations, total uncertainties are around 5% and uncertainties of (n,γ) cross sections are dominant. Those calculations are carried out with BWR pincell models, but it is also confirmed that results obtained with a BWR fuel assembly model are quite similar to those in the pincell models.