A back stop for a crane connectable to an up-down body which is attached to a crane main body so as to be capable of going up and down and connectable to the crane main body to prevent the up-down body from falling down, the back stop for a crane comprising: an outer casing which has an outer casing base end portion turnably connectable to one of the up-down body and the crane main body, and an outer casing front end portion arranged on a side opposite to the outer casing base end portion, and is formed with an opening portion opened in the outer casing front end portion; and an inner casing which has an inner casing base end portion turnably connectable to the other of the crane main body and the up-down body, and an inner casing front end portion arranged on a side opposite to the inner casing base end portion and to be inserted into the outer casing from the opening portion, and is slidably fitted in the outer casing, characterized by an inner greasing tube which is arranged inside one casing out of the outer casing and the inner casing and greases a slide portion between an outer circumference surface of the inner casing front end portion and an inner circumference surface of the outer casing, wherein the inner greasing tube includes: an injection portion which is arranged, on a base end portion side out of an outer casing base end portion side or an inner casing base end portion side of the one casing, outside of the one casing, and is formed with an inlet opened for accepting grease; a guide portion connected to the injection portion and disposed in the one casing; and a discharge portion connected to the guide portion and attached to the inner casing front end portion, and is formed with a discharge port opened to allow the grease having passed through the guide portion to be discharged into the outer casing. an outer casing which has an outer casing base end portion turnably connectable to one of the up-down body and the crane main body, and an outer casing front end portion arranged on a side opposite to the outer casing base end portion, and is formed with an opening portion opened in the outer casing front end portion; and an inner casing which has an inner casing base end portion turnably connectable to the other of the crane main body and the up-down body, and an inner casing front end portion arranged on a side opposite to the inner casing base end portion and to be inserted into the outer casing from the opening portion, and is slidably fitted in the outer casing, characterized by an inner greasing tube which is arranged inside one casing out of the outer casing and the inner casing and greases a slide portion between an outer circumference surface of the inner casing front end portion and an inner circumference surface of the outer casing, wherein the inner greasing tube includes: an injection portion which is arranged, on a base end portion side out of an outer casing base end portion side or an inner casing base end portion side of the one casing, outside of the one casing, and is formed with an inlet opened for accepting grease; a guide portion connected to the injection portion and disposed in the one casing; and a discharge portion connected to the guide portion and attached to the inner casing front end portion, and is formed with a discharge port opened to allow the grease having passed through the guide portion to be discharged into the outer casing. an injection portion which is arranged, on a base end portion side out of an outer casing base end portion side or an inner casing base end portion side of the one casing, outside of the one casing, and is formed with an inlet opened for accepting grease; a guide portion connected to the injection portion and disposed in the one casing; and a discharge portion connected to the guide portion and attached to the inner casing front end portion, and is formed with a discharge port opened to allow the grease having passed through the guide portion to be discharged into the outer casing.