To provide a lubricating structure for lubricating a pair of front and rear bearings supporting a draw roller and enabling easy installation of pipes.

A lubricating oil supplied from a trough 55 of a lubricating oil chamber 50 placed at the back of a frame 5 lubricates a rear bearing 25, passes through an oil-feeding channel formed by the inner surface of a cylindrical member 29, lubricates a front bearing 24 and returns to the lubricating oil chamber 50 via a pipe material 32 used as a return path. The return piping can be simplified by returning the oils integrally recovered with an oil pan 43 to an oil tank 52 compared with conventional method to separately install pipes to the front and rear bearings. Since the lubricating oil is supplied through one trough 55, only one feed pipe 57 is necessary for the connection of a pump 58 and the trough 55 and, accordingly, the installation of pipes can be simplified compared with conventional method.