To provide novel 3-(4-substituted aminophenylazo) pyrazolopyrimidin-7- one derivatives which are useful as black azo dyes.

The 3-(4-substituted aminophenylazo)pyrazolopyrimidin-7-one derivatives are represented by the formula (wherein R1-R3 are each independently a hydrogen atom, a halogen atom, an alkyl group, an aryl group, a cyano group, an acyl group, a carbamoyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyloxy group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, a sulfamoyl group or the like; R4 and R5 are each independently a hydrogen atom, an alkyl group or an aryl group; and R6-R9 are each independently a hydrogen atom, a halogen atom, an alkyl group, an aryl group, a carbamoyl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, a sulfamoyl group or the like).