Nanosecond laser ablation and subsequent ion formation processes of submicron aerosol particles containing multicomponent ammonium and sodium salts relevant to atmospheric aerosols were studied using a laser-ionization single-particle aerosol mass spectrometer. In the case of ammonium salts, chemical species with a low ionization energy are predominately observed in the positive-ion mass spectra, while those having a high electron affinity are predominately observed in the negative-ion mass spectra. Dissociative electron attachment processes take place. However, as far as sodium salts are concerned, the energetically preferred ions are not necessarily dominant, and the ion formation processes are suggested to be more complex than the ammonium salts.