The energy spectrum of primary cosmic rays above 10^17.0 eV has been updated from data collected with two extensive air shower arrays operating at Akeno, one with area 1 km² and the other with area 20 km². Along with the authors previous results in the lower energy region, the energy spectrum has been determined over about five decades of energy from 10^14.5 eV to 10^19.8 eV. A change in the index of the power-law energy spectrum is observed around 10^17.8 eV, as well as the usual features, namely the knee around 10^15.7 eV and the ankle around 10^19.0 eV. The indices of the differential power-law energy spectrum are: (2.62+or-0.12) below 10^15.7 eV, (3.02+or-0.03) for 10^15.7 approximately 10^17.8 eV and (3.16+or-0.08) for 10^17.8 approximately 10^18.8 eV. There is an indication of a flattening of the spectrum above approximately 10^18.8 eV with an index of (2.8+or-0.3). The flux above 10¹⁸ eV is (1.5 approximately 2.4)*10^-12 m^-2s^-1sr^-1 and is in good agreement with other experiments. The number of showers above 10^19.5 eV is seven for an exposure of 80 km² yr sr and further investigation by a new Akeno giant air shower array (AGASA), whose operation has started, is necessary to determine a cutoff energy in the spectrum, if any.