PURPOSE: To obtain the titled material capable of absorbing and releasing water vapor to retain the atmosphere of buildings etc. at a specified humidity, by putting a mixture of a combination of specific salt-saturated solution and crystal of said salt and highly water-absorptive resin and/or fiber therefrom in a water vapor-permeable container.

CONSTITUTION: The objective moisture-conditioning material can be obtained by putting a mixture of (A) a combination of salt-saturated solution giving specified water vapor pressure and crystal of said salt (e.g. BaCl2.2H2O) and (B) a highly water-absorptive resin and/or fiber therefrom (e.g. starch-acrylic acid graft polymer-based one) in a water vapor-permeable container (e.g. made of polyethylene).