To provide a device and a method for preventing rear-ender capable of shortening a braking distance at the actual braking time by transmitting a preceding vehicle a dangerous condition predicting rapid brake with wireless transmission, and receiving it and making a brake system into a brake action stand-by condition by a following vehicle.

This collision preventing device using inter-vehicle wireless communications includes an acceleration pedal sensor for detecting an operating condition of an acceleration pedal; a control unit judging a dangerous condition to output control signals; a wireless communication transmission and reception module for receiving the control signals from the control unit, and transmitting and receiving dangerous condition information between vehicles; a hydraulic control unit for receiving the control signals from the control unit, and maintaining the brake system in the brake action stand-by condition.