Laser light generated from laser light generating means (10) is fed through laser light transfer means (11) including a demagnification optical system (23) so as to be condensed in a part Ex where an object gas of analysis exists. The laser light is imparted with energy for causing a multiple photon excitation phenomenon or a multiple photon ionization phenomenon of gas in the condensed part Ex. The energy of the laser light is large enough for 17 eV or higher energy to be injected into a hydrogen molecule when the object gas of analysis is hydrogen and for 23 eV or higher energy to be injected into a helium atom when the object gas of analysis is helium. For example, the intensity of the laser light in the condensed part Ex is 10.sup.14 W/cm.sup.2 or higher. This provides a laser analytical instrument capable of observing various types of gas through an inexpensive and simple arrangement.