An object of the present invention is to provide a novel ethylene-α-olefin copolymer excellent in crosslinking properties; a foamed molded article having a low specific gravity and a low compression set (CS) and a composition capable of producing the foamed molded article, footwear parts composed of a foamed molded article; an ethylenic copolymer composition excellent in balance between weather resistance and mechanical strength, and an electric wire coating material and an electric wire sheath using the ethylenic copolymer composition; and a thermoplastic elastomer capable of producing a molded article excellent in balance between mechanical strength and toughness. The ethylenic copolymer (A) of the present invention is a copolymer composed of only ethylene and an α-olefin having 3 to 20 carbon atoms, and is characterized in that vinyl-group content (a) per 1000 carbon atoms as measured by infrared absorption spectroscopy, MFR10/MFR2.16 (b), and the specific gravity (c) are within a specific range.