The object is to provide a method for stabilization of a biological molecule and a composition, specifically a method for stabilization of an enzyme or a labeled antibody for use in a clinical diagnosis and a composition. Thus, disclosed is a method for stabilization of a biological molecule which is characterized by allowing (a) the biological molecule and (b) sericin and/or a hydrolysate or equivalence thereof to coexist with each other. Also disclosed is a composition having a biological molecule stabilized therein, which is characterized in that the components (a) and (b) coexist with each other in the composition. Further disclosed is a composition for stabilizing a biological molecule, which comprises sericin and/or a hydrolysate or equivalence thereof.