Apparatus and method for measuring water vapor permeability

A method for measuring water vapor permeability, which is characterized in that it comprises Measuring the water vapor permeability of a measured object based on a dew point temperature in a second room, which is measured after the introduction of steam into a first space, wherein the first space and the second space are separated by the measurement object, and wherein the first space is maintained at a predetermined temperature and a predetermined moisture under atmospheric pressure and the second space in a dry state with a dew-point temperature of -70 ° C or less under atmospheric pressure is maintained.