In accordance with the present invention, there is provided a bubble-containing ehtylene/.alpha.-olefin rubber excellent in kneadability, characterized in that the ethylene/.alpha.-olefin rubber prepared by copolymerization of 50-95 mol% of ethylene, 5-50 mol% of .alpha.-olefin having at least 3 carbon atoms and 0-10 mol% of non-conjugated polyene contains 5-1000 parts by volume, based on 100 parts by volume of said rubber, of bubbles and has a water absorption volume as measured in accordance with ASTM D 1506 of less than 20% by volume of the total bubble volume.