The present invention provides a sterol derivative or a pharmaceutically acceptable salt thereof having an activity to promote proliferation of neural stem cells. Namely, the present invention provides a sterol derivative represented by the general formula (I) (wherein Y represents optionally substituted lower alkyl or the like； X a and X b are the same or different, and represent a bond or the like； R 1 , R 2 , R 3 , R 4 , R 7 and R 8 are the same or different, and represent a hydrogen atom or the like； R 5 and R 6 are the same or different, and represent a hydrogen atom or the like； R 9 represents a hydrogen atom or the like； R 10 and R 11 together represent a bond or the like； and R 12 represents a hydrogen atom or the like) or a pharmaceutically acceptable salt thereof.
