Cross sections of 12,13C are evaluated for both neutrons and protons with incident energies up to 3 GeV. The evaluation is based on predictions from nuclear-model calculations and systematics as well as measurements. A nuclear-model calculation-code system is developed using the GNASH code for energies less than 150 MeV and the JQMD code for those above 150 MeV. The evaluated cross sections are as follows; neutron total cross sections, nucleon elastic scattering cross sections and angular distributions, nonelastic cross sections, production cross sections and double-differential cross sections of secondary light particles (n, p, d, t, 3He, α, and π) and gamma-rays, and isotope-production cross sections. The results are compared with available experimental data and the other evaluation.