The invention provides an epidermal basement membrane structure formation accelerating preparation and a skin external preparation comprising a serine protease inhibitor, and optionally an accelerator of production of extracellular matrix protein components of the epidermal basement membrane. It also provides, as a means for producing artificial skin having an adequately formed basement membrane, an artificial skin-forming medium which comprises a serine protease inhibitor, and optionally an accelerator of production of extracellular matrix protein components of the epidermal basement membrane and a matrix metalloprotease inhibitor, as well as a method for producing the same.