PURPOSE: To obtain an ethylene copolymer useful for packaging materials or the like, which has a specific melt flow index and gives a high strength film, by copolymerizing ethylene, a vinylester of a tert. satd. monocarboxylic acid and a copolymerizable monomer.

CONSTITUTION: The ethylene copolymer is obtained by copolymerizing ethylene, a vinylester of a tert. satd. monocarboxylic acid (e.g.; vinyl 2,2- dimethylpropionate or the like) and an another copolymerizable monomer (e.g.; methyl acrylate or the like) in the presence of a polymerisation initiator (e.g.; bis(2-ethylhexyl)peroxydicarbonate or the like) with heat in a stirring autoclave. The ethylene copolymer has 3-50 wt.% the vinyl ester of the tert. satd. monocarboxylic acid and optionally 5-30 wt.% the another copolymerized monomer based on the copolymer. And the copolymer has a melt flow index of 0.1-50 g/10 min. and gives a high mechanical strength film.