A molecular-beam apparatus with a spray-jet method was applied for the laser TOF-MS study of naphthalene derivatives, 2 naphthoic acid (2NA), and 1,5-dihydroxynaphthalene (DFIN). The results obtained by this method are compared with those obtained by the traditional sample-heating inlet method. The spray-jet method strongly improved the signal-to-noise ratio (S/N), compared to the traditional method. In addition, the intermolecular clusters due to hydrogen-bond formation were observed in case of the DHN system.