To discharge a fluid from a forward end part of a bar to a tip side even in the deep hole boring with simple constitution in a boring bar for boring.

The diameter of a body part 2 of a boring bar is smaller than the cutting diameter C of a tip 13. A fluid passage 5 is formed in a bar 1, and a branched passage 5a of the fluid passage 5 is opened in an outer circumferential surface of a forward end part of the body part 2. A discharging piece 8 in which a discharge port 8e is formed is fitted to the opening, and the fluid is discharged from the discharge port 8e from the tip 13 side. The diameter D of a projection of the discharging piece 8 is smaller than the cutting diameter C of the tip 13.