As pressure in a water tank rapidly rises when water inside a compressor is evaporated by the high temperature of compressed air and this situation makes the operation unstable, an object of the present subject matter is to address this problem. A water injected scroll air compressor is provided with: an air end (1) of the scroll air compressor; a driving unit (100) that generates driving force for enabling a rotary scroll component to rotate with repect to a fied scroll component; a compressing path from a suction port to a discharge port; a portion to inject water into the compressing path; a discharge piping of air discharged from the air end (1); a tank (105) provided on a path of the discharge piping for storing water separated from the compressed air; and a cooler (104) that is provided on the path of the discharge piping between the tank and the air end and cools the compressed air discharged from the air end.