PURPOSE: To provide a rotary atomizer cup excellent in durability, capable of eliminating or reducing the generation of air bubbles in atomized coating particles.

CONSTITUTION: This atomizing bell or a cup 16 for use in a rotary atomizing device has a generally frusto-conical-shaped wall having an outer surface and an inner flow surface 66, the tip of which terminates at an annular atomizing lip 68. A plurality of radially outwardly extending fins or ribs 74 are formed on the inner flow surface 66 of the cup 16 upstream from the atomizing lip 68, the ribs 74 are circumferentially spaced from one another to provide flow paths 85 therebetween for coating material flowing along the inner surface 66 of the cup 16. The coating material is divided into a number of individual streams 84 by the paths 85 before reaching the atomizing lip 68. These streams 84 are emitted from between adjacent ribs 74 a short distance upstream from the atomizing lip 68 which allows centrifugal force to at least partially flatten the streams forming ribbonlike streams, which, when flung outwardly from the atomizing lip 68, form completely atomized coating particles, substantially containing no air bubbles.