Atmospheric neutrino-fluxes are calculated over the wide energy range from 30 MeV to 3,000 GeV for the study of neutrino-physics using the data from underground neutrino-detectors. In this calculation, a full Monte Carlo method is employed for low energy neutrinos (30 MeV -3 GeV), while a hybrid method is used for high energy neutrinos (1 -3,000 GeV). At low energies, the ratio (νe +νe)/(νµ +νµ) agrees well with other calculations and is significantly different from observations. For the high energy neutrino-fluxes, the zenith angle dependence of atmospheric neutrino-flux is studied in detail, so that neutrino-oscillation parameters can be calculated for comparison with experimental results. The atmospheric muon-flux at high altitude and at sea level is studied to calibrate the neutrino-fluxes at low energies and high energies respectively. The agreement of our calculation with observations is satisfactory. The uncertainty of atmospheric neutrino-fluxes is also studied.