To provide a cabin back guard for a motor-truck capable of hardly generating rust on a lower end of a pipe member and enhancing durability and a commodity value.

The cabin back guard for the motor-truck is provided with the pipe member 10 formed to a shape corresponding to a peripheral edge shape of a cabin back panel; and a cap 20 relative to a lower end opening 10H of the pipe member 10, and is mounted to a back surface of the cabin back panel. The cap 20 is provided with a bottom wall 21 for covering the lower end opening 10H; a press-fitting part 13 projected from the bottom wall 21 and press-fitted to the lower end opening 10H; a standing up peripheral wall part 14 standing up from the bottom wall 21 and externally fitted to the lower end 7K of the pipe member 10; and water removal holes 15B-15E for flowing down and discharging water intruded between an outer peripheral surface 9M of a base part 9 of the press-fitting part 13 and an inner peripheral surface 14N of the standing up peripheral wall part 14.