To provide a three-way ball valve capable of suppressing the decrease of the total flow rate at the time of medium degree of opening.

The valve stem 1 of this three-way ball valve has a fit-in part 8, and at its front, an overhang part 14 is formed by extending the fit-in part 8 in the axial direction while its section shape is left unchanged, wherein the overhang part 14 is allowed to overhang from a through hole 9 in a valve ball 7 onto a flow passage in the valve ball so as to reduce mutual collision of fluids flowing in from the first opening 5 and second opening 6 and turbulence of the flow resulting from such a collision.