To provide a rear wheel drive type caterpillar device in an automobile in which caterpillar belts can be detachably fitted to the rear wheels during running.

Rear belt wheels 1 of smaller diameter than the tire T diameter of rear wheels R are borne in rotation free on the axle S inside both rear wheels R of an automobile so as to be close to the rear wheels. A front belt wheel 2 spacedly provided in front of the rear belt wheel 1 is pivotally fitted to a shaft mechanism A having a drive part operating by a command from a driver's seat on an automobile body side, and an endless belt 3 of which the back face 3a is formed into a belt shape conformed to the tread width of the tire T is laid over between the front belt wheel 2 and the rear belt wheel 1. This rear wheel drive type caterpillar device is constituted so that belt guide rollers 4, 5 are pivotally fitted to the shaft mechanism A at the upper part and the lower part nearby the rear belt wheel 1 in rear of the front belt wheel 2 so as to be movable following to the front belt wheel 2 and contacted with the back face 3a of the endless belt.