A collision preventing ECU 10 selects an obstacle point which has probability of colliding with an own vehicle, and calculates a collision time periods (TTC) of the obstacle point. When the minimum collision time period is equal to or shorter than a threshold time period, the collision preventing ECU 10 determines that a specific condition is established, and performs a collision preventing control to prevent the own vehicle from colliding with the an obstacle. When the obstacle which includes the obstacle point whose collision time period is minimum is a continuous structure, the collision preventing ECU 10 calculates a continuous structure angle, and memory a calculation number corresponding to an angle range within which a magnitude of the continuous structure angle falls. When there is no angle range whose calculation number is more than a threshold number, the collision preventing control is prohibited.