[Problem] To provide an ethylene-α-olefin copolymer that is highly effective in improving the molding properties of polyolefin resins and at the same time highly effective improving the balance between impact strength and stiffness.[Solution] Provided is an ethylene-α-olefin copolymer having a specific MFR, a specific density, and a specific molecular weight distribution, containing a suitable amount of a long-chain branching structure characterized by a branching index, and having a specific composition distribution structure characterized by solvent fractionation behavior.