A gas analysis device is provided with: a measurement unit that uses a plurality of measurement passes to measure the absorption amount of laser light including an absorption wavelength corresponding to at least two electron level transitions in the same component included in a combustion gas within a combustion furnace; a standard setting unit that sets a standard gas concentration distribution and a standard temperature distribution; and an analysis unit that determines a gas concentration distribution and a temperature distribution by solving a two-dimensional distribution function in which the gas concentration distribution and the temperature distribution are included as variables such that the minimum deviation between the actual measured absorption amount and a standard absorption amount is achieved.