UV laser-induced surface ionization with prism internal reflection is demonstrated to be a useful ion source for the Time-of-Flight mass spectrometer (TOF-MS). Spraying aniline (93 amu) on the prism surface and using 2 ns UV laser pulses, mass resolutions of 3,900 and 11,000 have been achieved in a linear TOF-MS and in a reflectron TOF-MS, respectively. Theoretical calculations indicate that mass resolution of over one million is possible, if a picosecond laser and appropriate electronics are employed.