The internal circulation liquid-liquid slug flow in microchannels intensifies mass transfer between the two phases. In this work, effectiveness of the slug flow in a narrow channel for the extraction of phenol from dodecane to water was first investigated. Extraction based on slug flow and that based on emulsion generated by a micromixer was compared from the viewpoint of the total operation time for extraction and separation of the two phases. The results showed that the enhanced circulation flow in slugs by increasing flow rate enables rapid extraction. Moreover, large slug length compared with emulsion diameter allows instant separation of the two phases after the extraction. Required time for extraction based on emulsion is shorter than that based on slug flow. However, it takes more than a few hours to separate the two phases due to the small emulsion size (∼50 μm). Thus, the extraction based on slug flow is preferable to that based on emulsion from the viewpoint of the total operation time for the entire extraction process. Then, the effects of operating parameters such as ratio of oil phase volume flow rate to total flow rate and outlet channel i.d. were examined. The result showed that appropriate operating condition improves extraction efficiency in slug flow.