(57) Nonwoven fabrics contain at least 30 % by weight of heat-­adhesive composite fibers consisting of core portion and sheath portion, said core portion being of the side-by-side type composite structure comprising two core components of different polypropylene base polymers in a composite ratio of 1:2 to 2:1, one of said core components having a Q value, expressed in terms of the weight-average molecular weight/the number-average molecular weight, equal to or higher than 6 and the other having a Q value equal to or lower than 5, and said sheath portion meeting at least the requirement that it should compirse a sheath component of a polyethylene base polymer having a melting point lower by at least 20 °C than the lower one of the melting points of said two core components. The nonwoven fabrics are bulky and soft due to the crimps of the heat-adhesive composite fibers resultant from the core portion and are stabilized by the inter-fiber bonds of the sheath portion.