An experimental investigation has been made on the flow separation characteristics of an air-warer two-phase slug flow into three successive capillary tubes with T-junctions. The flow pattern in the main tube just upstream of the branches was mostly limited to the slug flow in the present experiments. It was clarified that uneven separation of both phases among the three branches became large with decrease of flow rate at the outlet main tube. It was also clarified that the time ratio of the existence of water at the entrance of the branches was the dominant factor controlling the distribution characteristics of two-phase mixture into the branches. In some flow conditions. The slug flow and the annular flow were observed to alternatively change with time.