PROBLEM TO BE SOLVED: To provide water vapor permeable materials which are easy to adjust water vapor permeability and flexibility and excel in mechanical strengths, processability and the like. SOLUTION: The water vapor permeable materials are obtained by incorporating a hydrophilic compound into an ethylene/polar monomer copolymer having a polar monomer content of 10-50 wt.% and a water vapor permeability coefficient of >=0.005 g/m/day, and have a water vapor permeability coefficient of >=0.2 g/m/day. As the above polar monomer, a vinyl ester, an unsaturated carboxylic acid ester, an unsaturated carboxylic acid, an unsaturated carboxylic acid salt, and carbon monoxide are preferred.
