[en] Ion wave turbulence spontaneously excited in a current-carrying plasma is investigated by the microwave scattering method. The dispersion relation, the wavenumber spectra, and the angular spectra of the ion wave turbulence are determined from the angular distribution of the scattered wave. The wavenumber spectrum has a peak around k approx. = ν/subi/n/ v/subp/, and decreases as k/sup -4/.8plus-or-minus0.5 with increasing k, where ν/subi/n is the ion-neutral collision frequency and v/subp/ is the phase velocity of the ion wave. The angular spectrum of the wave energy is found to broaden as the total wave energy, W, increases along the electron drift. The effective collision frequency, ν/subf/, for electrons is also measured by the rf probe method as well as the dc method. An anomalous increase in ν/subf/ is observed with the increase in W along the electron drift. The present experimental results are consistent with the theory of perturbed ion orbits