A gyrating nozzle spray gun includes a grip including an air inlet, a valve seat, a gas-delivery tube connected to the valve seat and terminating in a mating connection portion and a trigger operable for letting external compressed air go into the air inlet and the gas-delivery tube, an attachment tube connected to the mating connection portion of the gas-delivery tube, and a gyrating pattern generator including a gas-supply tube connected to the mating connection portion and suspended in an accommodation chamber, a bearing mounted on a connecting portion, a coupling socket mounted on an outer race and a gyrating nozzle fastened to the coupling socket and rotatably disposed in an orifice and defining a gas accumulation chamber and an oblique jet hole for ejection of the intake flow of compressed air that goes through the air inlet, the gas-delivery tube and the gas-supply tube into the gas accumulation chamber.