An object of the present invention is to provide a method which constantly enables organ regeneration for the purpose of achieving organ regeneration with higher efficiency. It has been discovered that, in a blastocyst complementation method, a next generation is born when a deficiency in an organ, such as pancreas and kidney, is complemented by injection of ES cells into a generated blastocyst, and further discovered that a transgenic animal having a pancreas or a kidney thus complemented can transmit the phenotype to the next generation as a founder. This discovery has revealed that organ regeneration can be accomplished by using such a founder. Thus, the present invention achieved the above-described object.
