A determination device includes a single acceleration sensor for measuring an acceleration of a vehicle and a determination circuit for determining severity of a collision in an accident. A plastic deformation pulse detection section and an elastic deformation pulse detection section of the determination circuit detect a plastic deformation pulse and an elastic deformation pulse, respectively, from a waveform of measured accelerations. A severity determination section of the detection circuit determines the severity of a collision based on a correlation between a vehicle speed and a plastic deformation pulse, and a correlation between the vehicle speed, the plastic deformation pulse, and an elastic deformation pulse.