A transgenic rodent or its offspring which carries DNA having an exogenous caspase 1 gene integrated thereinto in such a manner as to express the gene specifically to the skin. The transgenic rodent of the present invention spontaneously develops atopic dermatitis in the absence of any specific pathogenic microorganism and is useful as a disease model animal. The transgenic rodent of the present invention is useful for developing preventive and/or therapeutic drugs for atopic dermatitis based on natural immunity and to clarify the onset mechanism of atopic diseases.