Fasudil-containing preparations that despite the use of a container excelling in the visibility of contents without particularly blocking of light, exhibit high stability against light and a method of improving the stability of the preparations against light, or storing the same. By regulating the pH value of aqueous solution of fasudil charged in a colorless transparent container to ≦ 5.5, there can be provided fasudil-containing preparations excelling in stability against light and can be provided a method of improving the stability of the aqueous solution of fasudil against light, or storing the same.
