The invention discloses quinazoline derivatives or salts thereof, which possess PDE9-inhibiting activity and are useful as treating agents of dysuria and the like, the derivatives being represented by the formula (I) in the formula, R 1 stands for phenyl or aromatic heterocyclic group which are optionally substituted with 1 - 3 substituents selected from halogen, C 1-6 alkyl, C 1-6 haloalkyl containing 1 - 6 halogen atoms and C 1-6 alkoxy； and n is an integer of 1 - 3.
