An electroslag welding wire containing, by mass% based on total mass of the wire: C: more than 0% and 0.07% or less; Si: more than 0% and 0.50% or less; Mn: more than 0% and 1.0% or less; Ni: 6.0 to 15.0%; Fe: 79% or more, and optionally at least one element selected from the group consisting of Cu, Cr, Mo, W, Nb, V and B, and satisfying the following relationship : 0.150 ≤ C + Si / 30 + W / 30 + Mn / 20 + Cu / 20 + Ni / 60 + Cr / 20 + Mo / 15 + Nb / 10 + V / 10 + 5 × B ≤ 0 .300 the electroslag welding wire further optionally containing at least one element selected from the group consisting of Ca, Mg, REM, Zr, Al and Ti, and satisfying the following relationship : 0.001 ≤ 1.6 Ca + Mg + 1.25 REM + Zr + Al + 0.8 Ti ≤ 0.70 and optionally, when the wire is a flux cored wire, the flux containing: a metal-based flux satisfying the aforementioned ranges of the composition; and a slag forming agent in an amount of more than 0% and not more than 15% based on total mass of the wire, wherein the slag forming agent contains at least one selected from the group consisting of SiO 2 , CaO, CaF 2 , BaF 2 , MgO, Al 2 O 3 , MnO, TiO 2 , ZrO 2 , FeO, Na 2 O, K 2 O, and BaO, and satisfies the following relationship : CaO + CaF 2 + BaF 2 + MgO + BaO + Na 2 O + K 2 O / SiO 2 + 0.5 Al 2 O 3 + TiO 2 + ZrO 2 + MnO + FeO ≥ 1.00 wherein the left side is taken as >100 when the slag forming agent does not contain any of SiO 2 , Al 2 O 3 , TiO 2 , ZrO 2 , MnO and FeO, the remainder of the electroslag welding wire being inevitable impurities. C: more than 0% and 0.07% or less; Si: more than 0% and 0.50% or less; Mn: more than 0% and 1.0% or less; Ni: 6.0 to 15.0%; Fe: 79% or more, and optionally at least one element selected from the group consisting of Cu, Cr, Mo, W, Nb, V and B, and satisfying the following relationship : 0.150 ≤ C + Si / 30 + W / 30 + Mn / 20 + Cu / 20 + Ni / 60 + Cr / 20 + Mo / 15 + Nb / 10 + V / 10 + 5 × B ≤ 0 .300 the electroslag welding wire further optionally containing at least one element selected from the group consisting of Ca, Mg, REM, Zr, Al and Ti, and satisfying the following relationship : 0.001 ≤ 1.6 Ca + Mg + 1.25 REM + Zr + Al + 0.8 Ti ≤ 0.70 and optionally, when the wire is a flux cored wire, the flux containing: a metal-based flux satisfying the aforementioned ranges of the composition; and a slag forming agent in an amount of more than 0% and not more than 15% based on total mass of the wire, wherein the slag forming agent contains at least one selected from the group consisting of SiO 2 , CaO, CaF 2 , BaF 2 , MgO, Al 2 O 3 , MnO, TiO 2 , ZrO 2 , FeO, Na 2 O, K 2 O, and BaO, and satisfies the following relationship : CaO + CaF 2 + BaF 2 + MgO + BaO + Na 2 O + K 2 O / SiO 2 + 0.5 Al 2 O 3 + TiO 2 + ZrO 2 + MnO + FeO ≥ 1.00 wherein the left side is taken as >100 when the slag forming agent does not contain any of SiO 2 , Al 2 O 3 , TiO 2 , ZrO 2 , MnO and FeO, a metal-based flux satisfying the aforementioned ranges of the composition; and a slag forming agent in an amount of more than 0% and not more than 15% based on total mass of the wire, wherein the slag forming agent contains at least one selected from the group consisting of SiO 2 , CaO, CaF 2 , BaF 2 , MgO, Al 2 O 3 , MnO, TiO 2 , ZrO 2 , FeO, Na 2 O, K 2 O, and BaO, and satisfies the following relationship : CaO + CaF 2 + BaF 2 + MgO + BaO + Na 2 O + K 2 O / SiO 2 + 0.5 Al 2 O 3 + TiO 2 + ZrO 2 + MnO + FeO ≥ 1.00 wherein the left side is taken as >100 when the slag forming agent does not contain any of SiO 2 , Al 2 O 3 , TiO 2 , ZrO 2 , MnO and FeO, the remainder of the electroslag welding wire being inevitable impurities. <EOS>