PURPOSE: To supply continuously a humidity-regulated carrier gas to the surface of a sample by providing a porous body in a humidity regulator, and bringing the carrier gas into contact with moisture.

CONSTITUTION: The gas pressure of a supply gas is regulated by a pressure regulating valve 1, and the flow rate is confirmed by a flow meter 2. Then the supply gas is introduced into a humidity regulator 5 which is dipped and fixed in hot water 4 contained in a thermostat 3. Water or an aq. saturated soln. of salts 6 is contained at the lower part of the humidity regulator 5, and a carrier gas introducing pipe 7 is inserted from the upper part. The gas outlet 8 at the end of the introducing pipe 7 is approached to the aq. soln. 6 to the extent that end does not touch the aq. soln. And a porous body 10 consisting of glass, etc. is provided to the end of the gas introducing pipe 7 to increase the contact area of the carrier gas with moisture generated from the aq. soln. 6.