This paper presents the first challenge for real time stiffness evaluation of red blood cell (RBC) by utilizing both a high speed vision and a micro channel. Since the passing time of cell in the micro channel whose diameter is smaller than that of cell depends upon the stiffness of cell, we can indirectly evaluate the stiffness by the passing time. With the assistance of a high speed vision system, we succeeded in evaluating the stiffness of RBCs with 5 [msec/cell]. The biggest advantage for utilizing a high speed vision is that we can know exactly what is actually happening in the channel, while it is really hard for other approaches. This paper discusses two key ideas for online sensing and shows experimental results.