Novel compounds or salts thereof, or crystals thereof, are provided which inhibit Axl and are useful for treating diseases caused by Axl hyperfunction, diseases associated with Axl hyperfunction and/or diseases accompanied by Axl hyperfunction. Pyridone derivatives represented by formula (1) having various substituents or salts thereof, or crystals thereof (where R 1 , R 2 , R 3 , R 5 , R 6 , A, W, X and n in the formula (1) are as defined in the specification, respectively) are provided.
