The Red Blood Cell (RBC) keeps a biconcave shape in a static fluid and deforms to a parachute shape in a flow. RBC membrane has been modeled by two kinds of springs coupled with fluid dynamics using a particle method. RBC shapes in a static fluid and a flow were simulated qualitatively. In this study, the Deformation Index of a flowing RBC is compared with the experiment. The calculation result shows good agreement with that of the experiment.