This paper describes the effects of a combustion-chamber corner on flame propagation into the ring crevice of a spark ignition engine. Because hydrocarbons from the engine can be reduced by flame propagation into the crevice, it is necessary to reveal flame behavior at the corner which dominates the flame propagation. We have conducted optical experiments of the flame propagation process toward the corner by the schlieren photography method. we have, furthermore, measured methane concentration at the corner and also at the side wall to calculate quenching distances. We have concluded the effect of the corner is greater than that of the side wall under a lean condition, based on the fact that the corner is about four times larger than the side wall in quenching distance when the equivalence ratio is 0.60.