In-line mixing that allows continuous stirring and mixture will be an important industrial process from the viewpoint of energy saving and space saving. Typical static mixers used for in-line mixing are normally designed for continuous flows and are effective for mixing only in the radial direction of the pipe. Such mixers cannot reduce the unevenness of concentration in the flow direction in in-line mixing processes involving intermittent injection using, for example, a metering pump. The purpose of this study is to reduce the unevenness in the flow direction in such an in-line mixing process. A new type of static mixer was developed based on the concept of dividing fluid flow into a plurality of fluid flow paths, which are recombined after a delay. Good results were obtained on the usefulness of the newly developed mixer.