The objective of the present study is to verify the atomization mechanism of a high-speed liquid steady jet through a simple hole nozzle which was proposed in a previous study. It showed that the atomization could be determined by the virtual injection velocity at the nozzle exit on the basis of the measurement of the droplet size and the discharge coefficient. Water was injected through various kinds of simple nozzles set on the basis of the consideration on the nozzle inside flow. The jet velocity was measured by a PDA, and the droplet size was measured by two optical sizing systems including PDA. The determining factor for the atomization could be successfully shown to be the jet velocity at the nozzle exit, and thus the proposed atomization mechanism could be verified.