The present invention relates to a human ADARB2-derived cell-penetrating peptide and a cargo-molecule delivery system using the same, and provides a method for delivering cargo molecules into a cell, the method comprising a step for bringing a cargo-molecule transduction domain including the human ADARB2-derived RMAD1 or a variant thereof and a recombinant cargo molecule fused with the cargo molecule transduction domain into contact with cells. The cargo molecule transduction domain of the present invention not only can introduce cargo molecules into cells at a higher efficiency than existing cell-penetrating peptides, but is a polypeptide sequence derived from human proteins, and thus also has no risk of causing immune response problems. Thus the cargo molecule transduction domain is useful for delivering various polymer materials into human cells.