The present invention provides a mouse with liver damage, having a high degree of damage against the mouse's original hepatocytes while having a uPA gene in a heterozygous form, and a method for efficiently preparing the mouse. Specifically, the method for preparing a mouse with liver damage having the uPA gene in a heterozygous form comprises the following steps of:(i) transforming mouse ES cells with a DNA fragment containing a liver-specific promoter/enhancer and cDNA that encodes a urokinase-type plasminogen activator operably linked under the control thereof;(ii) injecting the transformed mouse ES cells obtained in step (i) into a host embryo;(iii) transplanting the host embryo obtained in step (ii) via the injection of the ES cells into the uterus of a surrogate mother mouse, so as to obtain a chimeric mouse; and(iv) crossing the chimeric mice obtained in step (iii), so as to obtain a transgenic mouse in which the DNA fragment is introduced in a heterozygous form.