Disclosed is a water-injection type scroll air compressor whose pre-stopping operation time for drying can be reduced while enhancing compressor efficiency.The compressor body 1 includes a water supply line 24 for supplying water to a water feeder 23 connected to an air suction line 2. The water supply line 24 is provided with a control valve 27 that can control a flow rate of the water. A controller 28 conducts driving control of the control valve 27 in a 5×10−5 to 40×10−5 range of an injected-water volume ratio (more specifically, a volume ratio between an intake air flow rate and injected-water flow rate in the water feeder 23 of the suction line 2) and at the same time, in an injected-water volume ratio range of the compressor characterized so that an increase rate of overall adiabatic efficiency of the compressor per 1×10−5 increase rate of the injected-water volume ratio stays less than 2% of an original or initial value.