Provided are a synthetic peptide that induces the reprogramming of a differentiated cell, a reprogramming-inducing pharmaceutical composition that contains this synthetic peptide, and a method for producing an undifferentiated cell from a differentiated cell using this synthetic peptide. The peptide provided by the present invention is a synthetic peptide having a reprogramming-inducing peptide sequence formed of the amino acid sequence given by SEQ ID NO: 1 or a modified amino acid sequence thereof. The method for producing an undifferentiated cell provided by the present invention includes inducing the reprogramming of a target cell by culturing a cell culture which contains the target cell and to which the synthetic peptide has been supplied.
