To improve the riding comfortability by reducing a vibration transmitted from a main body frame to a cab, as well as preventing the swaying of the cab.

To each cantilever pillar 12 erected on a rotary frame 3, a frame body 14 is hung down and held through each first cushion holder 18, and while a cab 15 is held in the frame body 14 through each second cushion holder 19, each oil damper 20 to limit the swaying amount of the frame body 14 is provided between the frame body 14 and the rotary frame 3. Consequently, a vibration transmitted from the rotary frame 3 to the cab 15 is relaxed in two steps by the first cushion holder 18 and the second cushion holder 9, and as a result, the vibration of the cab 15 can be reduced. And by preventing the interferences of the frame body 14, the rotary frame 3, and each cantilever pillar 12 by each oil damper 20, the spring constant of each first cushion holder 18 can be set at a small value, and the vibration can be reduced effectively.