The present invention provides an Abelson kinase (Abl kinase) inhibitor which comprises, as an active ingredient, an indazole derivative represented by Formula (I) (wherein R1 represents substituted or unsubstituted aryl or a substituted or unsubstituted heterocyclic group) or a pharmaceutically acceptable salt thereof,an Abl kinase inhibitor which comprises, as an active ingredient, an indazole derivative represented by Formula (Ia) [wherein R2 represents CONR4aR4b (wherein R4a and R4b may be the same or different and each represents a hydrogen atom, substituted or unsubstituted lower alkyl, or the like, or R4a and R4b are combined together with the adjacent nitrogen atom thereto to form a substituted or unsubstituted heterocyclic group) or the like, and R3 represents a hydrogen atom, substituted or unsubstituted lower alkyl, or the like] or a pharmaceutically acceptable salt thereof, and the like.
