The present invention relates to the provision of a stable solid pharmaceutical composition containing an amorphous form of solifenacin or a pharmaceutically acceptable salt thereof and capable of inhibiting decomposition accompanied by long-term storage, to provide the medical field with a formulation of solifenacin or a pharmaceutically acceptable salt thereof. More particularly, the present invention relates to a solid pharmaceutical composition, comprising an amorphous form of solifenacin or a pharmaceutically acceptable salt thereof, and one stabilizer for amorphous solifenacin or two or more stabilizers for amorphous solifenacin, selected from the group consisting of citric acid or a pharmaceutically acceptable salt (excluding a calcium salt) thereof, sodium pyrosulfite, and a pharmaceutically acceptable salt of ethylenediaminetetraacetic acid.
