A rotary atomization head is provided, which prevents discharged threads of a coating material from making contact with each other and from being unified. A rotary head 1 includes: a diffusion surface 122 to diffuse the coating material toward an outer edge part 123 by centrifugal force; and a plurality of grooves 124 formed on the outer edge part 123. The plurality of grooves 124 extends in a radial direction. The adjacent grooves 124 have different depths. The grooves 124 have the same width.