To improve the characteristic of the ball side surface part of a ball valve apt to be subjected to a temperature rise failure by providing a passage for passing steam between the ball side surface of the ball valve and the body of the ball valve.

Steam is supplied from a steam inlet 8 and passed through a groove 9, and the condensed water of steam is discharged from a discharge port 10. At this time, it is necessary to lay out the steam inlet 8, the groove 9 and the discharge port 10 so that the condensed water not discharged from the discharge port 10 is not stayed in the passage of steam, and the steam is carried from above to down. Consequently, a temperature rise failure is reduced, whereby the production failure by bacterial contamination caused by the temperature rise failure can be reduced. The opening and closing frequency of the ball valve in sterilization can be reduced, and the life of the valve can be extended.