In the present study, we report experimental results obtained from air-water two-phase flows in the downstream region of a rotating pipe which consists of three independent rotating parts with a total length of 3m. The pressure drop characteristics associated with the change in flow behavior due to effect of the pipe rotation are examined. Particular attention is paid to the length of the rotating pipe on the pressure drop characteristics. From the results of experiment, it is revealed that the effect of the rotating pipe becomes significant in the downstream of the entrance. A correlation based on the consideration of bubble fusion number applied to the bubble fusion model (proposed in the previous report) can be used to estimate the friction multiplication factor φL2 satisfactory in bubble flow and plug flow regimes for the developed rotating two-phase flows.