Nucleon-Meson Transport Code of Japan Atomic Energy Research Institute version (NMTC/JAERI) was revised by implementing Lindhard-Robinson model and updating nucleon-nucleus total and non-elastic cross sections above 1 GeV so as to calculate displacement cross sections in the medium energy region of 20 MeV to 3.5 GeV. The displacement cross sections of Cr, Fe, Ni, and type 316 stainless steel were studied with the revised NMTC/JAERI. It is found that accurate treatment of the angular distribution with the optical model potentials gives reasonable displacement cross sections at tens of MeV. The applicability of the revised NMTC/JAERI code for the estimation of the radiation damage by medium-energy nucleons was supported by the comparison between the NMTC/JAERI and the LAHET calculation. The results of the NMTC/JAERI, however, were 20 % smaller than the values of Japanese Evaluated Nuclear Data Library (JENDL) PKA File at 20 MeV.