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, R1 stands for phenyl or aromatic heterocyclic group which are optionally substituted with 1-3 substituents selected from halogen, C1-6 alkyl, C1-6 haloalkyl containing 1-6 halogen atoms and C1-6 alkoxy; and n is an integer of 1-3.