PURPOSE: To obtain an ethylene polymer entirely consisting of an ethylene monomer, having a high die swell ratio, excelling in processability, etc., and being different from usual HDPE, L-LDPE or LDPE, a hydrogenation product thereof and a thermoplastic resin composition containing the same.

CONSTITUTION: An ethylene polymer entirely consisting of an ethylene monomer has a weight-average molecular weight (GPC, in terms of the molecular weight of the polyethylene) of 5000-2000000, satisfies the relationship: DR >0.5+ 0.125× logMw (wherein Mw is the weight-average molecular weight, and DR is the die swell ratio), has an energy of activation of melt flow (Ea) of 8-20kcal/mol and has a polymer main chain free from quaternary carbon atoms. An ethylene polymer is prepared by hydrogeneting the above polymer; and a thermoplastic resin composition containing the same are obtained.