In this study, using a spectrum average technique, the fission cross section of U-238 measured via the activation method at 5.0 MeV neutron energy. A comparison method was used in the measurement. The peak area of 537.3 keV gamma energy from Ba-140 fission product was compared with the peak area of 336.2 keV gamma energy from the In-115(n,n')In-115m reaction product. A correction was made for U-235(n,f). The fission cross section of U-238 was found as 527 +/- 69 mb.