To provide a method for producing a formed material such as yarn, film, sponge, etc., made of a composite comprising silk and cellulose and/or chitin or chitosan and to obtain amino acid polymer composite material such as yarn, film, sponge, etc., having the characteristic functions of these components.

Silk is dissolved in a mixed solution of three components of a halogenated alkali metal salt or alkaline earth metal salt, a lower alcohol and water and salts and the alcohol are removed by dialysis to give 2-20% silk solution. The silk solution, 3-10% cellulose solution by a viscose method and 2-10% solution of chitin or chitosan acylatesd derivative are used as a forming stock solution and spun, made into a film or molded into a sponge to give a polymer composite material such as yarn, film, sponge, etc.