A treadmill includes a tread deck supported on a tread base for rotatably supporting an endless belt, a motor driving device coupled to the endless belt for driving the endless belt to move around the tread deck, a lubricant supplying device having a container for containing a lubricant, a pump device attached to the container for pumping the lubricant out of the container, a motor coupled to an actuating rod for actuating the actuating rod toward and away from the pump device and to force the lubricant to flow out through the pump device, and a pipe is coupled to the pump device for receiving the lubricant from the container and for supplying the lubricant to lubricate the endless belt.