The present invention relates to an ultrahigh-molecular-weight ethylene copolymer powder having an intrinsic viscosity (η) of 10 dl/g to 34 dl/g, obtainable by copolymerizing ethylene and at least one olefin selected from the group consisting of α-olefins having 3 to 20 carbon atoms, cyclic olefins having 3 to 20 carbon atoms, compounds represented by the formula CH2═CHR1 wherein R1 is an aryl group having 6 to 20 carbon atoms, and linear, branched or cyclic dienes having 4 to 20 carbon atoms, wherein (1) a molded article of the copolymer powder has a haze of from 30% to 80% and (2) the copolymer powder has a bulk density of from 0.35 g/cm3 to 0.6 g/cm3.