A vehicle body strength adjusting system is provided in which a bumper beam includes a body portion which extends in a widthwise direction of a vehicle and inclined portions which extend from left and right opposite ends of the body portion and which are inclined in a longitudinal direction of the vehicle body. Further, the vehicle body strength adjusting system includes a variable crush-strength device which is disposed between the inclined portions of the vehicle body frames, which can be crushed when a collision with the vehicle occurs, and which has a variable crush-strength. A first bolt hole is formed in each of the inclined portions of the bumper beam and a second bolt hole is formed in the mounting bracket of the variable crush-strength device. At least one of the first bolt hole and the second bolt hole is an elongate hole. The first bolt hole and the second bolt hole are fastened to each other by a bolt.