Problem to be solved. To provide an aqueous sericin solution having excellent storage stability and to provide an enzyme inhibitor or an external preparation for skin containing the aqueous sericin solution. Solution. There is provided an aqueous sericin solution containing a compound represented by the following formula (1) and sericin, provided that when n in the above formula (1) is 0, the sericin has one or more bands in the molecular weight region of 150 kDa or more in SDS-PAGE. Where, R1 represents an alkylene group having 1 to 3 carbon atoms. R2 represents an alkyl group having 8 to 20 carbon atoms or an alkenyl group, n represents an integer of 0 or more and X+ represents a monovalent cation.