To obtain an ethylene/α-olefin copolymer resin having a specific density, a specific α-olefin content, a specific MFR, a specific mol.wt. distribution, or the like, having excellent molding processability, and useful for polyethylene pipes and joints.

This ethylene/α-olefin copolymer resin has (A) a density (ρ) of 0.945-0.60 g/cm3, (B) an α-olefin content (Y) of 0.30-1.50 mol.%, (C) a MFR (load: 5 kg, temperature: 190°C) of 0.25-0.50 g/10 min, (D) a mol.wt. distribution (an Mw/Mn ratio) of 25-40 determined by gel permeation chromatography, and (E) a ratio (R, wt.%) of the integrated elution amount of eluted components having mol.wts. of ≥100,000 and elution temperatures of ≤90°C to the total integrated eluted amount is not less than an equation: R0=17.37(Y)1.59 in the correlation of a mol.wt. - elution temperature - eluted amount which is determined by a cross fractionation of a temperature-rising elution fractionation with gel permeation chromatography.