Abstract: An apparatus for controlling stiffness of a vehicle body includes a slide member, a base member, a deformable member and an actuator. The slide member is disposed parallel to a direction of impact force acting on a first end of the slide member. The base member, which is disposed at a second end of the slide member, has a slit into which the slide member moves. The deformable member is disposed at the first end of the slide member. Both ends of the deformable member are connected to the base member and a cross section of the deformable member is substantially U-shaped. The actuator executes one of permitting the slide member to move into the slit and inhibiting the slide member from moving into the slit at a collision.