ABSfRACT There is provided a therapeutic agent for Alzheimer's disease for combined use of (S)-(2-methoxy-3,5-dimethylpyridin-4-y1)-1-(telmhydrofuran-3-y1)-1H-pyrazolo[4,3-c]qui noline-4(5H)-one represented by formula (1): 0 or a pharmaceutically acceptable salt thereof, and meniantine represented by formula (II): NH 2 ( H ) or a pharmaceutically acceptable salt thereof. 19