Abstract: A metal tube for reinforcing car body, and a car body reinforcement according to the invention have a curved portion extending over the entire longitudinal length or a local longitudinal length, wherein, when the reinforcement is assembled such that the outer periphery of the curved portion is aligned substantially in the direction of impact applied to the car body, the load ramp gradient, the maximum load and the absorbed energy are all enhanced in case of a car body collision. Particularly, an increase in the load ramp gradient as for the load property at the start of deformation provides an excellent crash capacity in reinforcing the car body. Moreover, the metal tube and the reinforcement according to the invention are capable of satisfying the current requirements for much more crash capacity of the car body, along with both a weight reduction of the car body and a reduced manufacturing cost, and therefore they are applicable in a wide field for protecting occupants in an automobile.