Abstract: A three-way ball valve having a valve body containing a valve chamber and three passages in T shape wherein two branch-like passages are for cold water and steam or hot water and the trunk-like passage is for outlet of warm water. A flow controlling ball valve of hollow mushroom-like construction consisting of a spherical part and a cylindrical part, is supported within the valve chamber rotatably about its valve stem axis which is perpendicular to the plane formed by the three passages. The hollow space is divided into two half-cylindrical rooms. Each room has a group of holes through the spherical shell for connecting the room to each inlet passage, and another group of holes through the cylindrical shell to the outside mixing room defined by the remaining space of the valve chamber wherein the flow controlling ball valve is placed. The two inlet fluids flow into the half-cylindrical rooms through the holes at the spherical shell functioning as flow controller, respectively.