A sodium iodide (NaI) solution in ethanol was introduced into a vacuum as a continuous liquid flow (liquid beam) and was irradiated with an ultraviolet laser beam. Ions ejected into the vacuum were mass-analyzed by a time-of-flight mass spectrometer. The mass spectra show that Na+(EtOH)(m) (m = 0-6) and Na+(NaI)(n)-(EtOH)(m) (n = 1-7) are ejected from the liquid beam. The results are interpreted as that these cluster ions are produced by unimolecular dissociation of nascent cluster ions composed of Na+ solvated with ethanol and/or (NaI)(n), which are born on the liquid surface. The dependence of the ion intensities on the NaI concentration indicates formation of NaI aggregates on the liquid beam surface in the entire NaI concentration range studied.