To provide a ceramic valve element for a ball valve, for selecting inexpensive porcelain material, and ensuring driving force contacting area with a stem without enlarging the diameter of a valve main element, also a stable floating ball funtion.

A projection 2, protruded on a flow passage 35 side at a dimension of 5-30% diameter of the passage 35, is provided on a part of a groove 4 for connecting the stem of a ceramic valve main element 1. The groove 4 preferably has a capsule-shape cross section penetrated to the passage 35 side of the main element 1, also the passage 35 of the main element 1 has a shape easily contracted toward the protruded part in the passage 35 direction of the main element 1 from the inlet part of the main element 1.