An isoquinoline-6-sulfonamide derivative represented by Formula, a salt thereof, or a solvate of the derivative or the salt: wherein R 1 and R 2 each independently represent a hydrogen atom, a halogen atom, a cyano group, an alkyl group, a halogenoalkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an alkylthio group, a hydroxyl group, a mercapto group, a nitro group, an amino group, an aminoalkylthio group, or a heteroaryl group; R 3 and R 4 each independently represent a hydrogen atom, an alkyl group, a hydroxyalkyl group, a dialkylaminoalkyl group, or an aminoalkanoyl group; R 5 represents a hydrogen atom, an optionally substituted alkyl group, an alkenyl group, an optionally substituted alkynyl group, an optionally substituted cycloalkyl group, or an optionally substituted alkanoyl group, or R 4 and R 5 may form a saturated heterocyclic ring together with the adjacent nitrogen atom, wherein the substituent on the alkyl group, the alkynyl group, the cycloalkyl group, or the alkanoyl group in R 5 is at least one substituent selected from (a) a cycloalkyl group, an aryl group, a heteroaryl group, an aryloxy group, a heteroaryloxy group, an arylene group, or a heteroarylene group optionally having, on the ring, at least one substituent selected from a halogen atom, a cyano group, an alkyl group, a halogenoalkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an alkylthio group, a hydroxyl group, an oxo group, a formyl group, an alkanoyl group, a carboxyl group, an alkyloxycarbonyl group, a mercapto group, a nitro group, an amino group, an urea group, a thiourea group, and an aminoalkyl group, (b) a hydroxyl group, (c) an oxo group, (d) an alkanoyloxy group, (e) an amino group, (f) a carboxyl group, (g) an alkoxy group, and (h) an alkyloxycarbonyl group; and A represents a linear or branched alkylene group having 2 to 6 carbon atoms and optionally having at least one substituent selected from a carboxyl group, a halogen atom, a cyano group, an oxo group, an alkenyl group, an alkynyl group, an alkoxy group, a hydroxyl group, an alkyloxycarbonyl group, an aminoalkyl group, an aryl group, a heteroaryl group, an optionally substituted aralkyl group, and an optionally substituted heteroarylalkyl group, wherein the aralkyl group or the heteroarylalkyl group in A optionally has at least one substituent selected from a halogen atom, a cyano group, an alkyl group, a halogenoalkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an alkylthio group, a hydroxyl group, an oxo group, a formyl group, an alkanoyl group, a carboxyl group, an alkyloxycarbonyl group, a mercapto group, a nitro group, an amino group, an urea group, a thiourea group, and an aminoalkyl group. R 1 and R 2 each independently represent a hydrogen atom, a halogen atom, a cyano group, an alkyl group, a halogenoalkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an alkylthio group, a hydroxyl group, a mercapto group, a nitro group, an amino group, an aminoalkylthio group, or a heteroaryl group; R 3 and R 4 each independently represent a hydrogen atom, an alkyl group, a hydroxyalkyl group, a dialkylaminoalkyl group, or an aminoalkanoyl group; R 5 represents a hydrogen atom, an optionally substituted alkyl group, an alkenyl group, an optionally substituted alkynyl group, an optionally substituted cycloalkyl group, or an optionally substituted alkanoyl group, or R 4 and R 5 may form a saturated heterocyclic ring together with the adjacent nitrogen atom, wherein the substituent on the alkyl group, the alkynyl group, the cycloalkyl group, or the alkanoyl group in R 5 is at least one substituent selected from (a) a cycloalkyl group, an aryl group, a heteroaryl group, an aryloxy group, a heteroaryloxy group, an arylene group, or a heteroarylene group optionally having, on the ring, at least one substituent selected from a halogen atom, a cyano group, an alkyl group, a halogenoalkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an alkylthio group, a hydroxyl group, an oxo group, a formyl group, an alkanoyl group, a carboxyl group, an alkyloxycarbonyl group, a mercapto group, a nitro group, an amino group, an urea group, a thiourea group, and an aminoalkyl group, (b) a hydroxyl group, (c) an oxo group, (d) an alkanoyloxy group, (e) an amino group, (f) a carboxyl group, (g) an alkoxy group, and (h) an alkyloxycarbonyl group; and A represents a linear or branched alkylene group having 2 to 6 carbon atoms and optionally having at least one substituent selected from a carboxyl group, a halogen atom, a cyano group, an oxo group, an alkenyl group, an alkynyl group, an alkoxy group, a hydroxyl group, an alkyloxycarbonyl group, an aminoalkyl group, an aryl group, a heteroaryl group, an optionally substituted aralkyl group, and an optionally substituted heteroarylalkyl group, wherein the aralkyl group or the heteroarylalkyl group in A optionally has at least one substituent selected from a halogen atom, a cyano group, an alkyl group, a halogenoalkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an alkylthio group, a hydroxyl group, an oxo group, a formyl group, an alkanoyl group, a carboxyl group, an alkyloxycarbonyl group, a mercapto group, a nitro group, an amino group, an urea group, a thiourea group, and an aminoalkyl group.