To provide a ball valve equipped with a steam trap which can complete a blow process in a short time by securing the area of a blow passage satisfactorily.

A ball valve element 2 provided with a T-form flow passage 6 is installed rotatably in a casing 1 which is equipped with an inlet 4 and outlet 5 at a right angle, and a steam trap 3 is furnished on one side of a long passage 11 in the T-form flow passage 6. The ball valve element 2 is rotated and the one side of long passage 11 is connected to the inlet 4, and a short passage 17 in the T-form flow passage is connected to the outlet 5 directed at a right angle to the inlet 4, and thereby a steam trapping function is established. The ball valve element 2 is rotated and the short passage 17 is connected to the inlet 4, and the other side of the long passage 11 is connected to the outlet 5, and thereby a blowing function is established in which a sufficient area of blow passage is secured between the inlet 4 and outlet 5. The ball valve element 2 is rotated and the inlet 4 or outlet 5 is blocked by the ball, and thereby a passage blocking function to shut the inlet 4 from outlet 5 is established.