The present invention is to provide a chicken LIF gene. Based on this genetic information, LIF protein derived from the chicken can be stably supplied and it solves the problems of the creation of transgenic chickens in the past. In addition, the present invention provides not only transgenic chickens for testing purposes but also supplies the first practical transgenic stock animals. The present invention relates to leukemia inhibitory factor (LIF) shown in sequence No. 2, and the gene that encodes thereof shown in sequence No. 1, and a manufacturing method of chicken LIF. In addition, the present invention pertains to a differential preventer of the chicken differentiable cell, and a method of chicken differential prevention and a culturing method for the chicken differentiable cell using thereof, and a medium comprising thereof.