The present invention relates to a transduced T cell precursor prepared by introducing a gene construct comprising a polynucleotide encoding C/EBP (CCAAT/enhancer binding protein) to a T cell precursor and overexpressing the C/EBP thereby, wherein the transduced T cell precursor is capable of differentiating into a regulatory T cell and an induced regulatory T cell differentiated therefrom. The transduced T cell precursor and the induced regulatory T cell may be useful for preventing and treating autoimmune diseases, inflammatory diseases and graft rejections caused by the malfunction of immune response.