When a thin flat plate is released in still air, the plate automatically sets into a rotational motion. This phenomenon is called autorotation. In this state, it is supposed that vortex shedding and unsteady fluid-dynamic forces interact each other. In this study, a discrete vortex method is used to found the effect of the vortex shedding on fluid dynamic forces acting on an auto rotating elliptic cylinder. By the calculation, it was found that the vortex shedding from the cylinder affects the fluid dynamic forces especially at the phases from -45 to -180 degree for drag coefficient and from -15 to -140 degree for lift coefficient.