To improve the operation reliability of a machine tool provided with a tool holder with coolant pipe in a simple structure.

A tool holder includes a conic hollow shank to be secured in a tool receiving section, which has an upper hole, and a coolant pipe 21, which is arranged in the hollow shank to supply coolant to a tool. The coolant pipe 21 includes a coolant entrance port 23 facing to the upper hole and an upper side pipe section 28 provided with a cylindrical outer side face 31, and when the holder is secured in the tool receiving section, a seal ring abuts on the side face of the tool receiving section. This seal ring, when abutting on the side face of the tool receiving section, is arranged in a coolant supply pipe, which partially get covered by the coolant pipe 21. A lid 35 is provided for the coolant entrance port 23, preventing cutting chips from reaching the inside of the coolant pipe 21. In addition, another pipe section 29 continues to the upper side section 28, and the outer diameter of this pipe section is smaller than that of the upper pipe section 28. When the tool holder is connected, the seal ring is in an area of the other section 29, and when the tool holder is secured, this seal ring closely abuts on the side face 31 of the upper pipe section 28 for the first time.