The present invention provides a quinolone compound represented by General Formula (1) or a salt thereof, wherein R1 represents a hydrogen atom, etc.； R2 represents a hydrogen atom, etc.； R3 represents a phenyl group optionally being substituted with one or more substituents, etc.； R4 represents a halogen atom； R5 represents a hydrogen atom or halogen atom； R6 represents a hydrogen atom； and R7 represents a hydroxyl group, etc. The quinolone compound have a functional improvement effect, which suppresses progression of neurological dysfunction by inhibiting the chronic progression of Parkinson's disease or protecting dopamine neurons from the disease etiology, thereby prolonging the period before first administration begins.本發明提供一種由通式(1)所表示的喹諾酮化合物：或其鹽，其中R1代表氫原子等等；R2代表氫原子等等；R3代表選擇性經一或多個取代基取代的苯基等等；R4代表鹵素原子；R5代表氫原子或鹵素原子；R6代表氫原子；及R7代表羥基等等。此喹諾酮化合物藉由抑制帕金森氏症的慢性發展或保護多巴胺神經元遠離疾病病原來抑制神經機能障礙發展而具有功能改善效應，因此延長在第一給藥開始前之時期。
