An atmospheric pressure, elevated temperature gas desorption apparatus which enables quanitiative analysis of impurities absorbed in or on the surface of a solid sample (semiconductor wafer, optical disc, etc.) is disclosed. The atmospheric pressure, elevated temperature gas desorption apparatus for desorbing impurities absorbed in or on the surface of a plate-like solid sample 18 into a carrier gas 19 in a chamber 6 under an atmospheric pressure while increasing the temperature of the solid sample 18 includes a desorption room 7A provided in the chamber 6 and connected through to a first gas supply system 1 for supplying the carrier gas 19, for desorbing impurities absorbed in or on the surface of the solid sample 18 into the carrier gas 19. A sample support room 7B is provided in the chamber 6 and is separated from the desorption room 7A by a partition member 6A. The solid sample 18 is in close contact with the partition member 6A. A heater 8 for heating the solid sample 18 is in close contact with the partition member 6A. A reserve room 9 is connected to the sample support room 7B and to a second gas supply system 13 for supplying a purge gas.