An electric resistance welded steel pipe for a line pipe, the steel pipe comprising a base metal portion and an electric resistance welded portion, wherein a chemical composition of the base metal portion consists of, in terms of % by mass: 0.030 to less than 0.080% of C, 0.30 to 1.00% of Mn, 0.005 to 0.050% of Ti, 0.010 to 0.100% of Nb, 0.001 to 0.020% of N, 0.010 to 0.450% of Si, 0.0010 to 0.1000% of Al, 0 to 0.030% of P, 0 to 0.0010% of S, 0 to 0.50% of Mo, 0 to 1.00% of Cu, 0 to 1.00% of Ni, 0 to 1.00% of Cr, 0 to 0.100% of V, 0 to 0.0100% of Ca, 0 to 0.0100% of Mg, 0 to 0.0100% of REM, and the balance being Fe and impurities, wherein: CNeq, expressed by the following Formula, is from 0.190 to 0.320, a ratio of % by mass of Mn to % by mass of Si is 2.0 or more, LR, expressed by the following Formula, is 0.210 or more, in a case in which a metallographic microstructure of the base metal portion is observed using a scanning electron microscope at a magnification of 1,000 times, an areal ratio of a first phase that is ferrite is from 40 to 80%, and a second phase, which is the balance, comprises tempered bainite, wherein the term bainite includes bainitic ferrite, granular bainite, upper bainite and lower bainite, a yield strength in a pipe axis direction is from 390 to 562 MPa, a tensile strength in the pipe axis direction is from 520 to 690 MPa, a yield ratio in the pipe axis direction is 93% or less, a Charpy absorbed energy in a circumferential direction of the pipe in the base metal portion is 100 J or more at 0°C, and a Charpy absorbed energy in the circumferential direction of the pipe in the electric resistance welded portion is 80 J or more at 0°C; CNeq = C + Mn / 6 + Cr / 5 + Ni + Cu / 15 + Nb + Mo + V LR = 2.1 × C + Nb / Mn wherein, in Formula and Formula, C, Mn, Cr, Ni, Cu, Nb, Mo, and V represent % by mass of respective elements. 0.030 to less than 0.080% of C, 0.30 to 1.00% of Mn, 0.005 to 0.050% of Ti, 0.010 to 0.100% of Nb, 0.001 to 0.020% of N, 0.010 to 0.450% of Si, 0.0010 to 0.1000% of Al, 0 to 0.030% of P, 0 to 0.0010% of S, 0 to 0.50% of Mo, 0 to 1.00% of Cu, 0 to 1.00% of Ni, 0 to 1.00% of Cr, 0 to 0.100% of V, 0 to 0.0100% of Ca, 0 to 0.0100% of Mg, 0 to 0.0100% of REM, and the balance being Fe and impurities, wherein: CNeq, expressed by the following Formula, is from 0.190 to 0.320, a ratio of % by mass of Mn to % by mass of Si is 2.0 or more, LR, expressed by the following Formula, is 0.210 or more, in a case in which a metallographic microstructure of the base metal portion is observed using a scanning electron microscope at a magnification of 1,000 times, an areal ratio of a first phase that is ferrite is from 40 to 80%, and a second phase, which is the balance, comprises tempered bainite, wherein the term bainite includes bainitic ferrite, granular bainite, upper bainite and lower bainite, a yield strength in a pipe axis direction is from 390 to 562 MPa, a tensile strength in the pipe axis direction is from 520 to 690 MPa, a yield ratio in the pipe axis direction is 93% or less, a Charpy absorbed energy in a circumferential direction of the pipe in the base metal portion is 100 J or more at 0°C, and a Charpy absorbed energy in the circumferential direction of the pipe in the electric resistance welded portion is 80 J or more at 0°C; CNeq = C + Mn / 6 + Cr / 5 + Ni + Cu / 15 + Nb + Mo + V LR = 2.1 × C + Nb / Mn wherein, in Formula and Formula, C, Mn, Cr, Ni, Cu, Nb, Mo, and V represent % by mass of respective elements. CNeq, expressed by the following Formula, is from 0.190 to 0.320, a ratio of % by mass of Mn to % by mass of Si is 2.0 or more, LR, expressed by the following Formula, is 0.210 or more, in a case in which a metallographic microstructure of the base metal portion is observed using a scanning electron microscope at a magnification of 1,000 times, an areal ratio of a first phase that is ferrite is from 40 to 80%, and a second phase, which is the balance, comprises tempered bainite, wherein the term bainite includes bainitic ferrite, granular bainite, upper bainite and lower bainite, a yield strength in a pipe axis direction is from 390 to 562 MPa, a tensile strength in the pipe axis direction is from 520 to 690 MPa, a yield ratio in the pipe axis direction is 93% or less, a Charpy absorbed energy in a circumferential direction of the pipe in the base metal portion is 100 J or more at 0°C, and a Charpy absorbed energy in the circumferential direction of the pipe in the electric resistance welded portion is 80 J or more at 0°C; CNeq = C + Mn / 6 + Cr / 5 + Ni + Cu / 15 + Nb + Mo + V LR = 2.1 × C + Nb / Mn wherein, in Formula and Formula, C, Mn, Cr, Ni, Cu, Nb, Mo, and V represent % by mass of respective elements.