We previously proposed a magnetic droplet-handling device for a micro-total analysis system (micro-TAS) and confirmed its operation principle. The device has the advantage of not requiring mechanical devices, such as pumps and valves, for handling solutions. Since then, we have further developed the biochemical reaction unit chip, which is a key component in our micro-TAS, by applying the droplet-handling mechanism. We confirmed that we could perform an enzymatic reaction without losing the enzymatic activity, by utilizing the alkaline phosphatase-catalyzed hydrolysis of p-nitrophenyl phosphate. We also confirmed that the obtained calibration curves for an enzyme immuno assay had linearity in the enzymatic reaction. We obtained a reaction efficiency of 70% on the reaction chip. From these results, we concluded that the developed reaction chip is applicable in enzyme immuno assay systems.