To provide a clamp holder capable of surely engaging a protrusion of a clamp piece into a central hole of a cutting throwaway tip when clamping.

The clamp holder 11 comprises a holder body 21 formed with an inclined surface 24, and a clamp piece 31 formed with a sliding surface 34 and a bolt insertion hole 35. The clamp piece 31 is pressed and fixed to the holder body 21 side by fastening a clamping bolt 41 screwed into a holder threaded hole 23. A coil spring 51 interposed between the clamp piece 31 and the holder body 21 energizes the clamp piece 31 in a separating direction from the holder body 21. A first locking part 52a is formed at the first end 52 of the coil spring 51, and a second locking part 53a is formed at the second end 53. The first locking part 52a is locked to a locked part 54 formed at the lower opening edge of the bolt insertion hole 35, and the second locking part 53a is locked to a second locked part 55 formed at the upper opening edge of the holder threaded hole 23.