A crash box for a vehicle may include a first plate having a middle end formed with a cylindrical first flange protruding in one direction, a second plate having a middle end formed with a cylindrical second flange protruding in another direction, a pipe having each of both ends coupled to the corresponding first and second flanges respectively, and an impact absorbing device configured to absorb an impact while the first flange and the pipe matched with each other through the impact absorbing device may be shear-deformed at a time of crash by pressing an overlapping portion of the first flange and one end of the pipe to deform shapes of a pressed portion of the first flange and the pipe into shapes matched with each other.