PURPOSE: To provide an inexpensive main spindle part control device with high reliabiliy capable of reducing remarkably the number of terminals provided between a hollow turning shaft and a support body.

CONSTITUTION: In a hollow rotary shaft 23, a controller 41 which is composed of various electric appliances such as a capacitor 57 and the like controlling a motor 24 based on the output information of a sensor 40, the sensor 40 and the motor 24 are accomodated. Substrates 58 to 60 supporting such electric appliances are also accomodated in the shaft 23 to form a triangle pole, while the electric appliances are supported on the substrates so that they may be opposite to the axial line side of the shaft 23.