A new type of micromixer for rapid mixing was developed based on mixing by utilizing both kinetic energy and molecular diffusion of fluids. The rapid mixing was realized by the collision of micro segments, which were divided into several streams in the radial, at the center of the mixer. From the results of conducting the Villermaux/ Dushman reaction and the precipitation of polymer particles by phase separation, it was clarified that the mixing performance of the developed micromixer was excellent, and the rapid mixing was driven by both the deformation of micro segments under high shear rate and instant molecular diffusion between micro segments. In addition, the mixer had a high throughput and corresponded to wide range of flow rate ratio of fluids. Thus, it is expected that the proposed design concept for the micro mixing will give us an efficient micro processing in future.