A method of producing induced pluripotent stem cells including a step for introducing an initialization factor into somatic cells of a mammal, and culturing in a neural stem cell culture medium to obtain induced neural stem cell-like cells, and a step for cultivating said induced neural stem cell-like cells in a growth medium to obtain induced pluripotent stem cells, wherein the initialization factor contains an OCT family, a SOX family, a KLF family, a MYC family, a LIN28 family and a P53 function inhibitor.