PURPOSE: To supply driving current not through a rotary joint by utilizing power of a traveling device to generate electricity, and providing a generator supplying power to a controlled device in a lower traveling body.

CONSTITUTION: When pressure oil from a hydraulic pump 10 of an upper turning body 1 is supplied to a hydraulic motor 21 of a lower turning body 2 through a dictional selector valve 11, a car is traveled. A gear 291 fixed to a rotary shaft of a subsidiary generator 29 is rotated through a first step gear 340 of a group of planet gears of a decelerator 34 decelerating rotation of the hydraulic motor 21, and power is generated in the subsidiary generator 29. In addition, power generated in the subsidiary generator 29 is supplied to a battery 36 and is stored, and it is supplied to a driving section driving a transmitting and receiving section, a tilt angle detection sensor and an electromagnetic driving section of a capacity control valve as a driving power supply.