Abstract: The present invention is a premixing-type spray gun which mixes a paint and compressed air inside the atomizing head and blows out the mixture as atomized from the spray hole. The inner and outer surfaces of the center hole in the atomizing head of the spray gun body are conical, and there is formed at the center of the cap having a nearly concentrical thickness at a lip-like aperture by providing a generally V-shaped recess from outside. Paint can be sprayed under a pressue of less than 1 kgf/cm.sup.2 with which the paint is less scattered, and the sprayed particle sizes can be made fine as with the conventional air spray guns.