[en] Studies on fission cross section measurements of Np-237 and Am-241 for transmutation were performed through the Kyoto University Lead Slowing-down Spectrometer (KULS) coupled to the 46 MeV electron linear accelerator (linac) at the Research Reactor Institute, Kyoto University (KURRI). The characteristics of the spectrometer KULS were firstly obtained for (1) the relation between neutron slowing-down time and energy. (2) energy resolution, and (3) neutron energy spectrum, by the continuous energy Monte Carlo code MCNP including time dependent process and by the experiments using neutron resonance filters and/or the linac time-of-flight method. Then, the KULS was applied to the fission neutron cross section measurements of Np-237 and Am-241 relative to that of U-235 from about 1 eV to about 10 keV with energy resolution (dE/E) of about 40%. The experimentally obtained results were compared with previously measured values and recent evaluated data files, ENDF/B-VI and JENDL-3. Although the shape of the present cross section of Np-237 agrees with that measured by Plattard et al. and with those in ENDF/B-VI and JENDL-3, the absolute values of above three are from 3 to 4 times smaller than those of the present data. However, the measurement by Hoffman et al. is rather closer to the present result. For Am-241, the absolute values of the evaluated data and the Dabbs' measurement are 3 times lower than the present data, which are rather closer to those measured by Gayther et al. and Bowman et al. above a few tens of eV. (author)