This paper presents modeling and simulation study of a simple planar passive walker with ankle springs, which exhibits double support phase. Contact model of the passive walking is constructed in order to deal with various conditions of contact with the ground and the presence of impact due to foot touchdown, liftoff and possibly foot rotation over the heel or toe during walking. A foot-ground contact is simulated as a compression normal force with Coulomb friction. Numerical simulations indicated that the passive walker with flat feet and ankle springs walks down stably on a shallow slope. copyright (c) 2010 by JSME.