An object of the present invention is to provide an
ethylene-.alpha.-olefin copolymer excellent in extrusion molding
processability and in the balance between the appearance and impact
strength. This object is achieved by a copolymer of ethylene and
.alpha.-olefin of from 4 to 20 carbon atoms having melt flow rate (MFR;
unit is g/10 minutes), melt tension at 190.degree. C. (MT; unit is cN),
intrinsic viscosity ([.eta.]; unit is dl/g), the chain length A and
characteristic relaxation time at 190.degree. C. (.tau.; unit is sec)
which satisfy the specific relations.