A polypeptide hydrogel of the present invention is a hydrogel of a polypeptide derived from spider silk proteins, and has a moisture content of 85.0 to 99.9 mass % based on 100 mass % of the polypeptide hydrogel. A method for producing the hydrogel includes: a solution production step in which a polypeptide derived from spider silk proteins is dissolved in at least one dissolving solvent selected from the group consisting of: (A) dimethyl sulfoxide; (B) dimethyl sulfoxide with an inorganic salt; and (C) N, N-dimethylformamide with an inorganic salt, so as to obtain a solution of the polypeptide; and a substitution step in which the solution produced in the solution production step is substituted with a water-soluble solvent. Thus, the present invention provides a polypeptide hydrogel having excellent water retentivity and a polypeptide hydrogel suitable for application to a living body.