In order to establish a means for producing functional cells such as [beta] cells in the body of an animal such as a pig, the present invention provides a method for developing a secondary organ using a non-human animal in which formation of an organ is inhibited. The method includes a step of raising a newborn or fetus of a non-human animal, in which formation of an organ is inhibited, by at least supplementing a portion of the function of the organ for which formation is inhibited.本發明係以確立於豬等動物體內製作β細胞等功能細胞之方法為目的，提供一種使用器官形成受阻之非人類動物使二次器官發育之方法，其包括對上述器官形成受阻之非人類動物之新生仔或胎仔補充形成受阻之上述器官之功能之至少一部分而加以培育之步驟。
