PURPOSE: To stabilize the grinding accuracy of a work with a cooling efficiency being improved, by forming a hole or groove with a heating body or the body to be heated arranged adjacent to the heating body being formed with its being divided in plural plates, and composing a cooling passage with the plural plates being Joined.

CONSTITUTION: A heating body 7 or the body to be heated arranged adjacent thereto in a machine tool is formed with its division in plural plates 13a-13h, and also holes 14b-14h, 15b-15h, 16b-16h, 17c-17h, 18h or grooves in the specified shape are formed so that the cooling efficiency may rise based on the temperature distribution of the heating body 7 or the body to be heated on the plural plates 13a-13h. A cooling passage is composed by the holes 14b-14h, 15b-15h, 16b-16h, 17c-17h or grooves of each plate with the plural plates 13a-13h being joined, and coolants 19a, 19b are flowed to this cooling passage. The grinding accuracy of a work can thus be stabilized with the cooling efficiency being improved.