A polypeptide composition induces a pluripotent stem cell culturing property, particularly, an excellent cell growth ability. The polypeptide composition contains a predetermined polypeptide including an amino acid sequence of human vitronectin or an amino acid sequence of a predetermined first region derived from human vitronectin. The polypeptide composition includes a multimeric polypeptide, which is composed of two or more monomers held together by intermolecular cross-linking via cysteine residues included in the first region, in an amount equal to or less than 20% by mass of a total mass of polypeptides contained in the composition. A culture method for pluripotent stem cells includes culturing pluripotent stem cells in the presence of the polypeptide composition. Also provided is a culture vessel including a support which has a cell culture surface and the polypeptide contained in the polypeptide composition disposed on the cell culture surface of the support.