A paper feeding tractor including a frame formed by a pair of said frames; a driving sprocket rotatably supported between both side frames at a first end portion of the frame; an endless belt adapted to be driven by the driving sprocket; a pair of first supporting rollers located at a second end portion of the frame and arcuate guiding members projecting from the opposite inner surfaces of the side frames at the second end portion for supporting said endless belt in a loop, whereby the endless belt is arcuately supported by the first supporting rollers and the arcuate guiding members; and a second supporting roller rotatably supported between both side frames at a longitudinal position between the driving sprocket and the first supporting rollers to support the inner peripheral surface of the end belt. The arcuate guiding members are designed to support both side edge portions of the inner peripheral surface of the endless belt, while the second supporting roller is designed to support the transversely central portion of the inner peripheral surface of the endless belt.