Provided is a resin composition containing polymethallyl alcohol (A) having a repeating structural unit represented by the following formula (1) in an amount of greater than or equal to 30 mol %, and a metal ion (B), a content of the metal ion (B) being greater than or equal to 0.05 μmol per 1 g of the polymethallyl alcohol (A); a method of producing the resin composition; and a molding containing the resin composition.