Abstract: A breathable and liquid-impervious composite sheet includes a flexible, breathable and liquid-impervious thermoplastic synthetic resin film and heat-sealable nonwoven fabric layers placed upon opposite surface of the film. The film has a basis weight of 0.098˜0.392 N/m2 and a thermal shrink percentage of 3˜18% under 60° C. thermal atmosphere while the nonwoven fabric layers 3A, 3B have a basis weight of 0.049˜0.294 N/m2. The sheet is formed with plural arrays of heat-sealed regions each extending in transverse direction Y and spaced one from another in longitudinal direction X intersecting the transverse direction Y. 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 the film.