PURPOSE: To limit an area to be observed and measured so that the desorption of an object adsorbed to the surface of a solid material caused by a temperature rise produced by heating can be accurately measured by coating the solid material with an adsorptive inert film except a surface area to be measured and desorbing the object from the surface area by heating the solid material, and then, measuring the desorbed species.

CONSTITUTION: A solid material 11 is coated with an adsorptive inert film 12 except a surface area to be measured and an object adsorbed to the surface area is desorbed by a temperature rise produced by heating, and then, desorbed species are detected. For example, the bottom surface section, side face section, and edge section of the upper surface of a sample composed of a silicon substrate 11, which are excluded from the object of measurement, are coated with a silicon oxide film 12 and the substrate 11 is put in a vacuum vessel 21. When the temperature of the substrate 11 is raised in the vessel 21 at a rate of 5-10°C/sec after evacuating the vessel 21 with an evacuating device 24, hydrogen molecules are desorbed from the substrate 11 within the temperature range from 400°C to 600°C. When the total amount of desorbed hydrogen molecules is found by detecting the molecules with a residual gas analyzing tube 23 and recording the detected molecules, the adsorbed amount of hydrogen to the uncoated part of the substrate 11 coated with the silicon oxide film 12 can be found.