It is revealed that an organ such as pancreas can be regenerated by utilizing a fact that the deficiency of an organ is complemented by injecting an induced pluripotent stem cell (iPS cell) into a developed blastocyst in a blastocyst complementation method. Thus, the present invention has solved the above-described object. This provides a method for producing a target organ, using an iPS cell, in a living body of a non-human mammal having an abnormality associated with a lack of development of the target organ in a development stage, the target organ produced being derived from a different individual mammal that is an individual different from the non-human mammal.
