Disclosed is a novel means which makes it possible to steadily mass-produce knockout individuals even in large animals. The method of the present invention is a method for producing a non-human large mammal or fish (non-human animal) that produces gametes originating in a different individual, and comprises transplanting at least one pluripotent cell derived from a second non-human animal into an embryo derived from a first non-human animal, said embryo being at a cleavage stage and having a genome in which a function of nanos3 gene is inhibited, to prepare a chimeric embryo, and allowing said chimeric embryo to develop into an individual. When a pluripotent cell having a genome in which a desired gene is knocked out is used as the pluripotent cell derived from the second non-human animal, the first non-human animal capable of producing germ cells in which the desired gene is knocked out is obtained, and therefore knockout non-human animals can easily be mass-produced by mating such non-human animals.
