The measurements have been made of the wind waves generated on opposing currents in a wind wave channel which is equipped with a water circulation system. Since what obtained directly using fixed wave gauges were the apparent wave spectra, they were transformed into the true spectra by calculating the theoretical wave velocity to the first order approximation for the experimental velocity distributions including considerable drift currents. The true spectra seemed to be reliable for the low frequency part, though they revealed some inconsistency at the high frequency part.
　The dominant wave's lengths for each fetch were estimated from the true spectra and they were found to be much larger in the cases with opposing currents than those without currents. However, this was simply because the considerable waves already existed at the windward end of the channel with opposing currents and the growth rates of the wave length with increasing fetch were not very different between the two cases. H1/3 evaluated from the total power of spectra were also larger with opposing currents than without current, but their growth rates were conversely smaller in the former cases than the latter.