An upper electrode used for a substrate processing apparatus using plasma is provided. The upper electrode includes a bottom surface including a center region and an edge region having a ring shape and surrounding the center region, a first protrusion portion protruding toward plasma from the edge region and having a ring shape, wherein the first protrusion portion includes a first apex corresponding to a radial local maximum point toward the plasma, and a first distance, which is a radial-direction distance between the first apex and a center axis of the upper electrode, is greater than a radius of a substrate.