The present invention relates to compounds which have a potent Rho-kinase inhibitory action and which are useful as therapeutic agents for treating diseases, such as hypertension, pulmonary hypertension, cerebral vasospasm, angina pectoris, cardiac failure, arteriosclerosis, glaucoma, dysuria, asthma, and erectile failure, and drugs containing the compounds. The present invention provides a 4-haloisoquinoline derivative represented by formula (1): an acid-added salt thereof, or a solvate of any of the foregoing, in which X is halogen, such as fluoro, chloro, bromo and iodo.