Provided are: a cultured tuna having a lower selenium content compared to natural tunas； a method for rearing the same； a processed food of the cultured tuna having a low selenium content； and a method for manufacturing the processed food. The cultured tuna which has either of muscles with a selenium content of 90 μg/100 g or less or liver with a selenium content of 1400 μg/100 g or less, the edible parts of the same and a thermally processed food which contains the edible parts. The method for rearing the cultured tuna comprises feeding the tuna with a formula feed continuously for 30 days or longer, said formula feed comprising an inner capsule in which a fish meal containing 30 wt% or more of sardine meal and a fat or oil are enclosed and an outer coating which coats the inner capsule and is formed of at least one material selected from the group consisting of a protein and a polysaccharide.
