Abstract: This invention provides a novel means that allows efficient secretion and production of a target protein in a host cell. This invention concerns a novel polypeptide having an activity of improving the secretion productivity of a target protein, a gene comprising a nucleotide sequence encoding such polypeptide, a vector comprising such gene, a transformant obtained by transforming a host cell with such vector, and a method for producing a protein comprising a step of culturing such transformant and recovering a target protein from the culture product.