Provided is an electric-resistance-welded steel pipe for line pipes, wherein: a base material part contains, in terms of mass%, at least 0.03% and less than 0.10% of C, 0.30-1.00% of Mn, 0.010-0.100% of Nb, and 0.010-0.500% of Si, with the balance consisting of Fe and impurities, has a CNeq value of 0.12-0.25, has an Mn/Si ratio of 2.0 or more, and has an LR value of 0.25 or more; a metal structure of the base material part has a ferrite ratio of 80-98%, with the balance structure consisting of pearlite and/or bainite, has a hardness difference [balance structure - ferrite] of 50-100 Hv, and satisfies YS 360 MPa or more, TS 465 MPa or more, and YR 0.90 or less; and the Charpy absorbed energies of the base material part and an electric-resistance-welded part at 0°C are both 100 J or more. CNeq = C + Mn/6 + Cr/5 + (Ni + Cu)/15 + Nb + Mo + VLR = (2.1C + Nb)/Mn
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