One of the drag-reducing technics in the pipe flow is microbubble injection. However, the drag reduction effect of microbubble injection into water flows often remains unclear, including their mechanisms. In addition, there are very few reports on drag reducing effect of microbubble injection into water pipe flows. This paper describes the experimental results of water-microbubble two phase flows in a horizontal pipe. The flow was visualized by using a high-speed camera and green laser sheet light. The streamline velocity profile was measured by using PIV and LDV system. As experimental results of the friction factor and velocity profile by using PIV, the drag reducing effect of microbubble injection was not observed in this experiment. The flow characteristics were quite similar to water single phase flow in this experiment.