The present invention relates to non-human animal embryonic stem cells in which a lecithin:cholesterol acyltransferase-like lysophospholipase endogenous gene is inactivated; non-human animals deficient in expression of LLPL gene; methods of screening for prophylactics and/or therapeutic drug using the cells or the animals; and prophylactics and/or therapeutic drug obtainable by the screening.The non-human animal ES cells of the invention in which their LLPL gene is inactivated are very useful in creating non-human animals deficient in expression of LLPL gene. The LLPL expression deficient non-human animals of the invention can be disease models for such diseases caused by insufficiency of the biological activities of LLPL since the animals lack various biological activities inducible by LLPL. Therefore, the animals of the invention are useful in screening for prophylactics and/or therapeutic drug for various diseases resulting from LLPL deficiency, as well as in elucidating the causes of LLPL-related diseases and examining therapeutic methods for such diseases. The screening methods of the invention are capable of efficiently screening for prophylactics and/or therapeutic drug for various diseases resulting from LLPL deficiency.