To provide a safety device for a vehicle improved to safely protect occupants in any type of collision.

The safety device 1 for a vehicle is constructed mainly of a structure (front frame 7) with a member (variable-rigidity member) capable of varying its rigidity abruptly; sensors 3 for detecting physical quantities concerning the vehicle; and a control portion 9 for receiving signals from the sensor 3. The control portion 9 determines the condition of the vehicle from signals of the sensor 3 and calculates the degree of rigidity which should be imparted to the variable-rigidity member in order to optimize the deformation of the structure associated with the progress of the condition. The control portion then sends a rigidity variation signal to the member and controls the actuation of an occupant restraint device 5 such as a seatbelt or an airbag in association with the actuation of the variable-rigidity member.