Abstract: There is provided a thermally bonded nonwoven fabric with a unit weight of 10 to 40 g/m.sup.2, comprising 20 to 100% by weight of a composite fiber with a fineness of 0.5 to 8 denier and 80 to 0% by weight of other fibers as the constituent fibers, the composite fiber comprising a first component which is an ethylene-.alpha.-olefin copolymer composition comprising an ethylen-.alpha.-olefin copolymer containing 0.5 to 4% by weight of an .alpha.-olefin having 4 to 12 carbon atoms blended with 0.01 to 0.3% by weight of a phenol type antioxidant and 0.01 to 0.3% by weight of a sulfur type antioxidant, having a Q-value (weight average molecular weight/number average molecular weight) of 4 or less, a density of 0.930 to 0.950 g/cm.sup.3, a melt flow rate of 5 to 50 g/10 min. and an oxidation induction time at 210.degree. C. of 10 min. or longer, and a second component which is a thermoplastic resin having a melting point higher by at least 20.degree. C.