Breathable and liquid-impervious composite sheet

A breathable and liquid-impervious composite sheet comprising a flexible, breathable and liquid-impervious thermoplastic synthetic resin film and heat-sealable fibrous nonwoven fabric layers placed upon opposite surfaces of said synthetic resin film, and obtained by heat-sealing said synthetic resin film and said fibrous nonwoven fabric layers together in the course of a heat treatment process including an embossing roll, wherein:

• said synthetic resin film has a basis weight of 0.098˜0.392 N/m2 and a thermal shrink percentage of 3˜18% under 60° C. (±5° C.) thermal atmosphere while said nonwoven fabric layers have a basis weight of 0.049˜0.294 N/m2, wherein the sheet is formed with plural arrays of heat-sealed regions 4 each extending in transverse direction of said composite sheet and spaced one from another in longitudinal direction intersecting the transverse direction and wherein, between each pair of the adjacent heat-sealed regions, the nonwoven fabric layers describe circular arcs which are convex outward in a thickness direction of the sheet from the opposite surfaces of said synthetic resin film.