Abstract: A ball valve for controlling liquid flow that comprises a tubular valve body, a ball rotatably built-in inside of the valve body, a pair of unions screwed into opposite ends of the valve body so as to be in slidable contact with the ball, and a pair of body caps connected to outer ends of each union through a packing ring for providing a water-tight seal therebetween. This valve have no cavities therein which cavities tend to entrap the liquid during the passage thereof. According to this construction the valve is kept always clean and free from any contamination caused by the putrescence of the entrapped liquid, even when used in the food industry.