In the present study the relation between cavitation inside a multi-hole mini-sac nozzle and the progress of the liquid jet atomization was analyzed by means of a quantitative image analysis of transient cavitation in the injector and the atomizing spray. The unsteady string cavitation forming inside the sac and wall cavitation in an orifice of a transparent three-hole injector model were captured using a high-speed camera, and the deforming and atomizing liquid jet was visualized using a synchronized high-speed camera simultaneously. In order to clarify the relation between cavitation and the liquid jet atomization, string cavitation in the sac and cavitation in the orifice were evaluated by introducing cavitation index I-c (z; t). The atomization characteristics of the liquid jet were evaluated by using the atomization index I-a and the width of the spray B-s along the spray axis. The spatio-temporal analysis of these three indices clarified that the appearance of string cavitation is correlated with the reduction in wall cavitation length in the nozzle hole and enhances the atomization of the spray. The present achievement by means of quantitative spatio-temporal analysis may contribute to establishing new design approaches of high-performance fuel injectors.