An effective microdevice for extraction has been developed, which is made of acrylic resin for visualization and ease of handling and extracts oil contents from the aqueous phase into the organic phase by using slug flow. The performance of this microdevice was evaluated by carrying out the extraction of sun flower oil from the aqueous phase into the hexane phase. In the case of a volume ratio of 1 : 1 for the sample and hexane, the extraction effciency reached 68.9% when the total flow rate was 0.4 mL/min (4.0 x 10(-7) m(3)/min) and the residence time was 144 s. The generated slug flow was kept stable at shorter residence times, while the generated slug flow became unstable at longer residence times. In the case of a volume ratio of 1 : 2 for the sample and hexane, the extraction effciency reached 87.3% when the total flow rate was 0.3 mL/min (3.0 x 10(-7) m(3)/min) and the residence time was 192 s. The generated slug flow was less stable overall and the slug droplets were observed to partially unite with each other in the downward flow. These flow rates were larger on submilli-L/min (10(-7) m(3)/min) order and it was easy for this microdevice to handle in terms of the used flow rate ranges. Moreover, this microdevice included not only the slug flow generation area but also the extraction area of oil contents and aqueous/hexane phase separation area. Furthermore, the extraction time per experimental condition was about 8 min and much faster than that with the batch method of the hexane extraction method (at least 2-4 h). Therefore, the microdevice for extraction in this study was found to be effective for improving extraction effciencies.