Abstract: A moisture-proof paper sheet comprising a moisture-proof coating layer formed on a paper sheet substrate and comprising (a) a moisture-proof, film-forming synthetic resin (for example, carboxyl-modified SBR resin), (b) plate crystalline phyllosilicate compound particles with an average size of 5 to 50 .mu.m and an aspect ratio of 5 or more and (c) a moisture-proofness-enhancing agent, for example, urea-formaldehyde condensation reaction products, organoalkoxysilane compounds, or polyamidepolyurea compounds, has an enhanced resistance to water vapor permeation and, after use, the waste moisture-proof paper sheet can be easily re-pulped and recycled.