This invention provides a method for preparing a brown adipocyte from a somatic cell of a mammal by introducing at least one brown adipocyte-related gene or expression product thereof and at least one reprogramming-related gene or expression product thereof into the somatic cell, the brown adipocyte-related gene being at least one member selected from the group consisting of PRDM16(P) and C/EBPβ(C), the reprogramming-related gene being at least one member selected from the group consisting of Myc family genes (c-Myc(M), N-Myc, L-Myc(L), S-Myc, and B-Myc), GLIS family genes (GLIS1 (G), GLIS 2, and GLIS 3), Klf family genes (KLF1, KLF2, KLF3, KLF4(K), KLF5, KLF6, KLF7, KLF8, KLF9, KLF10, KLF11, KLF12, KLF13, KLF14, KLF15, KLF16, and KLF17), Oct family genes, Sox family genes, and Lin-28.
